ASVAB Electronics

What is the frequency of Direct Current (DC)? A.)0 Hz B.)50 Hz C.)60 Hz D.)100 Hz

A.)0 Hz Frequency is the number of occurrences of an event per unit time and can be expressed as Hz. In DC, the charges flow steadily in one direction while charges keep switching directions in AC. Since no switching (events) occur with DC, the frequency is zero.

A microwave is consuming 800 W power using a standard North American 120 V power supply. What is the approximate amount of current flowing? A.)3 amperes B.)5 amperes C.)7 amperes D.)9 amperes

C.)7 amperes The formula for finding electrical power is Power = Voltage x Current or P=VI. Rearranged we have I = P/V = 800/120 = 6.67 ? 7 amperes

Which of the following is the most conductive element? A.) Gold B.) Silver C.) Aluminum D.) Copper

B.)Silver The most conductive material is Silver followed by Copper and Gold.

How much current will flow through the resistor R2 if R1=R2=10 ohms and R3=20 ohms? A.)1.5 amperes B.)3 amperes C.)4 amperes D.)6 amperes

(A.) 1.5 amperes The circuit in the given figure is a series circuit. We know that the same current flows through all the resistors connected in series. The equivalent resistance of the given circuit = R1+R2+R3 = 10+10+20 = 40 ohms.

What is commonly used in a circuit in which the flow of electricity needs to pass easily in one direction but not the opposite direction? A.)Resistor B.)Diode C.)Capacitor D.)Inductor

B.)Diode A diode is a two terminal (i.e. anode and cathode) electrical equipment which conducts electrical current in one direction only.

Which of the following is not an application of a transistor? A.)Electric Switch B.)Amplifier C.)Transformer D.)Current Regulator

C.)Transformer A transistor is a semi-conductor device designed to amplify and switch electronic signals and electric power. A transistor has a wide range of applications including electric switch, amplifier, voltage and current regulator etc. A transistor is different from a transformer, a transistor is a semi-conductor device while a transformer is an electromagnetic device.

Which of the following is a unit of power? A.)J/s B.)W C.)V.A D.)All of the above

D.)All of the above Power is the rate of doing work i.e. Power = Work/time = J/s. Electrical power is described as P=VI and the unit of power is Watt (W). Power is the product of current and voltage, so it can also be written as V.A where V represents the voltage and A represents the current.

Which of the following statements is correct? A.)A generator converts mechanical energy into electrical energy. B.)A motor converts electrical energy into mechanical energy. C.)A motor converts mechanical energy into electrical energy. D.)Both options A and B

D.)Both options A and B The operation of a motor is opposite to that of a generator. A generator converts mechanical energy into electrical energy and the motor converts electrical energy into mechanical energy.

Which of the following statements is correct? A.)Conventional current flows from positive terminal of the source to its negative terminal through the circuit. B.) Electron current flows from positive terminal of the source to its negative terminal through the circuit. C.)Conventional current flows from negative terminal of the source to its positive terminal through the circuit. D.)Both options A and B.

A.) conventional current flows from positive terminal of the source to its negative terminal through the circuit. Electron flow is the flow of electrons which actually occurs in a circuit. The electron current flows out of the negative terminal of the source through the circuit to its negative terminal. The conventional current was chosen as a convention at the time of discovery of electric currents, it assumes that the flow of current is out of the positive terminal of the source through the circuit to its negative terminal.

A fuse rated at 0.8 A blows when the switch is closed. If an 80 V supply is supplying power to the circuit, what would be the maximum possible value of the resistance for which the current flows through the circuit? A.)100 ohms B.)90 ohms C.)80 ohms D.)70 ohms

A.)100 ohms The fuse is rated at 0.8 A which means that the current will continue flowing through the circuit when the current is limited to 0.8 A. According to ohm's law, I=V/R. First option will give I=80/100=0.8 A which is the rated voltage and the current will flow through the circuit. For second, third and fourth options, currents are I=80/90=0.89, I=80/80=1 A and I=80/70=1.14 A which are greater than the rated current.

How many valence electrons are present in most semi-conductor materials? A.)4 B.)5 C.)6 D.)7

A.)4 Most semi-conductor materials have four valence electrons making them neither good conductors nor good insulators. For example, silicon and germanium are both semi-conductors and they have four electrons in their valence shells.

A ground is not one of the following. A.)A place with a maximum resistance. B.)A place of lowest potential in a circuit. C.)A reference point in the circuit from which voltages are measured. D.)A common return path for electric current.

A.)A place with a maximum resistance. A ground is also called the earth in an electrical circuit. A ground is a place of lowest potential and least resistance in an electrical circuit. Ground/Earth is also a reference point in an electrical circuit from which voltages are measured and a common reference path for electric current.

Which of the following statements is correct regarding inductors? A.)An inductor blocks AC but allows DC to pass. B.)An inductor blocks DC but allows AC to pass. C.)An inductors blocks both AC and DC. D.)An inductor allows both AC and DC to pass.

A.)An inductor blocks AC but allows DC to pass. An inductor resists a change in current that is why it blocks AC. The equation of an inductor is (di)/(dt) = V/L. If you apply DC across an inductor, it will stabilize to some current flow based on the maximum current available from the current/voltage source. In this mode, the inductor presents very low resistance, so it can be said that it allows DC to pass.

A capacitor stores energy in the form of: A.)Electric Field B.)Magnetic Field C.)Both Electric and Magnetic Fields D.)Neither Electric nor Magnetic Field

A.)Electric Field A capacitor stores electrical energy in the form of electric field because the DC source creates and excess of electrons on the negative plate and a shortage of electrons on the positive plate. The electrostatic attraction between the positive and negative charges keeps the charge intact in the capacitor, even when the voltage source is removed.

The generated force on a current carrying wire can be increased by A.)Increasing the amount of current flowing. B.)Decreasing the length of the wire. C.)Decreasing the strength of the magnetic field. D.)All of the above

A.)Increasing the amount of current flowing. The generated force on a current carrying wire is directly proportional to the amount of current flowing, the length of the wire, and the strength of the magnetic field. Increasing any of these will increase the force on the wire and the capacity to do work.

What would happen to the voltage if the current doubles and the resistance increases four times? A.)The voltage will increase 8 times. B.)The voltage will increase four times. C.)The voltage will increase two times. D.)The voltage will remain same.

A.)The voltage will increase 8 times. Ohm's Law states that V=IR. If current doubles and the resistance increases four times then V=(2I)(4R)=8(VI) i.e. the voltage increases 8 times.

Which of the following statements are correct regarding a Voltmeter? A.) A voltmeter is used to measure current. B.) A voltmeter is used in parallel to a circuit. C.) A voltmeter must have the least resistance. D.) All the above

B.) A voltmeter is used in parallel to a circuit. A voltmeter is used to measure the potential difference between two points. It is used in parallel with a circuit when measuring voltage. Ideally a voltmeter should have high resistance so that no current flows through it while measuring the potential difference between the two points.

Which of the following statements is incorrect regarding Ohm's Law? A.) Voltage is directly proportional to the current. B.) Voltage is inversely proportional to the resistance. C.) Current is inversely proportional to the resistance. D.) Voltage is directly proportional to both current and resistance.

B.) Voltage is inversely proportional to the resistance. Ohm's law states that V=IR. According to the law, voltage is directly proportional to both current and resistance while current is inversely proportional to the resistance.

Four capacitors are connected in parallel, each having a capacitance of 4 farads. What will be the equivalent capacitance of these capacitors? A.)4 F B.)16 F C.)2 F D.)1 F

B.)16 F Capacitors are added in parallel. In the given question, four capacitors (each having 4 F capacitance) are connected in parallel then their equivalent capacitance would be 4+4+4+4=16 F.

A series circuit is shown in the figure. What is the voltage across resistor R3 if R1=20 ohms and R3=30 ohms? A.)6 V B.)9 V C.)12 V D.)15 V

B.)9 V The voltage will be divided in two resistors connected in series. The voltage across the resistor R3 is (15)(30/20+30) = 9 V

What are the three terminals of a transistor? A.)Ground, Emitter, Collector B.)Base, Emitter, Collector. C.)Base, Anode, Cathode. D.)Ground, Anode, Cathode.

B.)Base, Emitter, Collector. A transistor has three connectors or terminals which are the base, the emitter and the collector. The flow of charge goes in the collector, and out of the emitter, depending on the charge flowing to the base.

What does the following image represent? A.)Transistor B.)Diode C.)Heater D.)Transformer

B.)Diode The given image represents a diode. A diode is a two terminal electrical equipment which conducts electrical current in one direction only.

An ideal fuse should have a: A.)High melting point and a low current rating. B.)Low melting point and a high current rating. C.)High melting point and a high current rating. D.)Low melting point and a low current rating.

B.)Low melting point and a high current rating. The ideal fuse should carry its rated current indefinitely and it should melt quickly on small excess of the current.

What does the following image represent? A.)Fixed Resistor B.)Rheostat C.)Capacitor D.)Potentiometer

B.)Rheostat The figure given represents a Rheostat. A Fixed Resistor is a resistor having a fixed or defined resistance. A variable resistor is a resistor which is used to control the current by varying the resistance. There are two types of variable resistor: rheostat and potentiometer. A rheostat has two usually two terminals (one fixed and the other moveable) while a potentiometer has three terminals (two fixed and one moveable).

The electric power consumed by an electric kettle is 2000 W. If the voltage being supplied to the kettle increases 4 times and the current flowing through the kettle is decreased by half, what would be the effect on the power consumed by the kettle? A.)The electric power would remain the same. B.)The electric power would double. C.)The electric power would increase 4 times. D.)The electric power would increase 8 times.

B.)The electric power would double. The formula of finding electrical power is P=VI. If the voltage increases 4 times and the current flowing through the kettle becomes half then P = (4V)(1/2)I = 2(PI). The electric power of the electric kettle would become double.

A resistor with a 100 ohms of resistance has 10% tolerance. What does this mean? A.)The resistor has a fixed resistance of 100 ohms. B.)The resistance may vary from 90 ohms to 110 ohms. C.)The resistance may vary from 90 ohms to 100 ohms. D.)The resistance may vary from 100 ohms to 110 ohms.

B.)The resistance may vary from 90 ohms to 110 ohms. Tolerance of a resistor indicates how much the measured value of a resistance is different from its theoretical value, and is calculated using percentages. 10% tolerance means that the resistance can be 100?10. A 100 ohms resistor with 10% tolerance may have values ranging from 90 ohms to 110 ohms.

If two different resistors are connected in series, then which of the following statements is correct regarding the electrical power consumed by the resistors? A.)The power consumed by each resistor will be the same. B.)The resistor offering larger resistance will consume more electrical power. C.)The resistor offering smaller resistance will consume more power. D.)The power consumed by each resistor cannot be determined unless the current flowing through each resistor is given.

B.)The resistor offering larger resistance will consume more electrical power. If two resistors are connected in series then the current flowing through each resistor is the same because the current remains the same in a series. The formula of finding electrical power is P=VI. From ohms' law, we know that V=IR ? I=V/R. Putting the value of I in the formula of electrical power will give P=R(I)^2. As current is same through both resistors then electrical power is directly proportional to the resistance i.e. the bigger the resistance the higher will be the power consumed and vice versa.

Which of the following is true regarding an AC signal? A.)The greater the time period, the greater the frequency. B.)The smaller the time period, the greater the frequency. C.)The time period of an AC signal is directly proportional to the square of the frequency. D.)There is no relation between the frequency and time period of an AC signal.

B.)The smaller the time period, the greater the frequency. Frequency is the number of occurrences of an event per unit time. The relationship between the frequency and time period of an AC signal is f=1/T i.e. frequency is inversely proportional to the time period of an AC signal. The smaller the time period, the greater the frequency of the signal.

Four bulbs are connected in a series-parallel circuit as shown in the given figure. Each bulb is exhibiting a resistance of 4 ohms. If one of two bulbs in the parallel connection blows up, then what will the effect be on the total effective resistance offered by all the bulbs? A.)The total effective resistance will decrease. B.)The total effective resistance will increase. C.)The total effective resistance will remain same. D.)The circuit would be open.

B.)The total effective resistance will increase. The resistances are added in series. The equivalent resistance offered by two bulbs in parallel connection would be ((1/4)+(1/4))^-1 = 2. The effective resistance offered by all the four bulbs in this case is 4+2+4 = 10 ohms. If one of the bulbs in parallel connected blows up then the effective resistance offered by all four bulbs would be 4+4+4=12 ohms. Therefore, the effective resistance will increase.

A circuit breaker is better than a fuse because... A.)Circuit breakers are less expensive. B.)A circuit breaker responds more quickly to an excessive current than a fuse. C.)A circuit breaker can be reused multiple times. D.)A circuit breaker is often not compatible with modern electric equipment.

C.)A circuit breaker can be reused multiple times. A circuit breaker is better than a fuse because it can be reused multiple times unlike a fuse which needs to be replaced once it is blown.

Which of the following statements is correct? A.)Atomic Number is the number of electrons present in any material. B.)Atomic Number is the number of neutrons present in any material. C.)Atomic Number is the number of protons present in the nucleus of any material. D.)Atomic Number is the number of protons and electrons present in any material.

C.)Atomic Number is the number of protons present in the nucleus of any material. Atomic number is also called the proton number. It is the number of protons present in the nucleus of any material.

A capacitor is also known as: A.)Inductor B.)Rectifier C.)Condenser D.)Switch

C.)Condenser A capacitor is a passive two-terminal electrical equipment used to store electrical energy electrostatically in an electric field. It is also known as a condenser.

The electrical symbol in the figure represents which of the following? A.)Oscilloscope B.)Lamp (Lighting) C.)Galvanometer D.)Ammeter

C.)Galvanometer The given electrical symbol represents a galvanometer. A galvanometer is a type of sensitive ammeter. It is an instrument for detecting electric current.

Copper is a good conductor of electricity because: A.)It has a high melting point. B.)It does not corrode. C.)It demonstrates a low amount of resistance. D.)It is inexpensive.

C.)It demonstrates a low amount of resistance. Flow of electrons (electric current) is inversely proportional to the resistance. The material exhibiting the least resistance will be a good conductor of electricity. That is why copper is a good conductor of electricity.

An inductor stores energy in the form of A.)Electrical field B.)Mechanical Energy C.)Magnetic field D.)Both electrical and magnetic fields.

C.)Magnetic field When a current is flowing through an inductor, an energy is stored in the form of magnetic field. The formula of energy stored in an inductor is: Energy=(1/2)LI^2.

A parallel combination of two resistors is connected in series with a 4 ohm resistor. If the total effective resistance by these three resistors is 10 ohms then which of the following can be the values of two resistors in parallel connection? A.)Each resistor is of 6 ohms. B.)One resistor is of 12 ohms and the other is of 24 ohms. C.)One resistor is of 8 ohms and the other is of 24 ohms. D.)One ohm is of 16 ohms and the other is of 24 ohms.

C.)One resistor is of 8 ohms and the other is of 24 ohms. The resistances are added in series. The effective resistance offered by a combination of two resistors in series with a 4 ohms resistor is 10 ohms which means that the equivalent resistance of two resistances in parallel connection must be 6 ohms. Suppose one resistor is "a" ohms and the other resistor is "b" resistors then the equivalent resistance will be (ab/a+b) = 6. Therefore, 8 ohms and 24 ohms resistors will be the correct answer.

Which of the following statements is incorrect regarding a transformer? A.)The frequency does not change in transformation action. B.)A transformer has no mechanical losses. C.)Secondary current of a step-down transformer is less than its primary current. D.)The power on primary side of an ideal transformer is equal to the power on secondary side.

C.)Secondary current of a step-down transformer is less than its primary current. A transformer is a static device so it has no mechanical losses. A transformer only transforms the voltage and the current and the frequency remains same during the transformation process. The power on primary side of an ideal transformer is equal to the power on the secondary side. It the transformer is step-down then the voltage on secondary side must be less than the voltage on its primary side which means that the current on secondary side must be higher than the current on its primary side.

Rectification is an important application of a diode. Rectification can be defined as: A.)The conversion of DC into AC. B.)Boosting AC. C.)The conversion of AC to DC. D.)Boosting DC.

C.)The conversion of AC to DC. Rectification is an important application of a diode. It is the conversion of alternating current (which reverses its direction periodically) to a direct current (which flows in only one direction).

Current I is passing through a load of resistance R. If the voltage across the load doubles and the resistance of the load is reduced by half then what is the amount of current passing through the load? A.)0.5I B.)I C.)2I D.)4I

D.)4I According to Ohm's law, the relationship between voltage, current and resistance is V=IR which can be rearranged as I=V/R. If the voltage doubles and the resistance is reduced by half then I1=(2V)/(0.5R)=4(V/R)=4I. Therefore, the current flowing through the load will increase four times.

In a transformer... A.)The primary coil is the one that is connected to the source. B.)The secondary coil is the one in which an electric current is induced. C.)A larger number of secondary coils means a larger voltage. D.)All of the above

D.)All of the above A transformer uses the properties of an inductor to transform the level of voltage in a circuit. AC flowing in wires wrapped around an iron core magnetizes the core, and in turn produces a changing magnetic field on the core. This changing magnetic field generates a voltage in a neighboring coil of wire. Depending on the number of turns on the wire in the primary versus the secondary coil, a smaller or larger voltage can be induced in the secondary coil.

A capacitor blocks Direct Current (D.C). Hence, it is also known as a: A.)Blocking Capacitor B.)Switched Capacitor C.)Coupling Capacitor D.)Both Blocking and Coupling Capacitors

D.)Both Blocking and Coupling Capacitors A blocking capacitor is also called the coupling capacitor. It is used to block the passage of flow of direct current (D.C) from one circuit to another by giving alternative passage to flow.

What is the basic operation of a step-up transformer? A.)It steps up the voltage. B.)It steps down the current. C.)It steps up the current. D.)Both options 1 and 2

D.)Both options 1 and 2 The basic operation of a transformer is to step up or step down the voltage in the circuit. If the transformer is a step up then it will step up the voltage and step down the current to maintain the power (i.e. P=VI) in primary and secondary sides of the circuit.

Current flows: A.)From Higher Potential to Low Potential. B.)Towards least resistance. C.)Towards maximum resistance. D.)Both options A and B

D.)Both options A and B Current is the flow of charges from higher potential to lower potential and current always takes the path of least resistance.

What does the following image represent? A.)Inductor B.)Transistor C.)Diode D.)Ground

D.)Ground The given symbol represents an earth ground which is used for zero potential reference and electric shock protection.

If three different resistors are connected in parallel and a voltage is applied across them, which of the following statements is correct? a.)The smallest resistance has the least power loss across three resistances. b.)The greatest resistance has the maximum power loss across three resistances. c.)Both the smallest and the greatest resistances have the same power losses. d.)The greatest resistance has the least power loss across three resistances.

d.)The greatest resistance has the least power loss across three resistances. *If three different resistances are connected in parallel and a voltage is applied across them then the voltage is same across all the resistances. The formula for finding power is P = VI = V(V/R) = (V^2/R). According to the formula, the resistor with the least value will have the maximum power loss and the resistor with the maximum value will have the least power loss.

What is the total amount of energy if a 12 C charge produces 3 V? A.)0.25 J B.)4 J C.)12 J D.)36 J

D.)36 J Voltage is defined as one joule per coulomb i.e. V=J/C ? J=VC ? J=12?3=36 J

Which of the following instruments is used to measure resistance of a load? A.) Voltmeter B.) ohmmeter C.) Ammeter D.) Galvanometer

B.) ohmmeter An ohmmeter is a device which is used to measure electrical resistance. A voltmeter is a device which is used to measure voltage differences between two points in a circuit. An ammeter is a device which is used to measure electric current flowing through a circuit. A galvanometer is a more sensitive ammeter which is used to measure electric current flowing through a circuit.