Aircraft Mechanic - Block IV (Basic Electricity)

When the total capacitance of a certain circuit containing three capacitors with capacitances of .25 microfarad, .03 microfarad, and .12 microfarad, respectively? (Note: Ct= C1+C2+C3) A. .04pf B. .4uF C. .04uF

B. .4 uF

A 12v electric motor has 1,000w input and 1 horsepower output. Maintaining the same efficiency, how much input power will a 24v, 1-horsepower electric motor require? (Note: 1 hp = 746w) A. 500w B. 1,000w C. 2,000w

B. 1,000w 1000w produces 1 HP 1000w produces 746 @ 1HP = 746w 1000w x N = 746 746/1000 = N N= .746 Motor is 74% efficient 1HP = 746w 746/.746 = 1000w

(Fig 13) Determine the total current flow in the circuit. A. 0.2a B. 1.4a C. 0.8a

B. 1.4a

(Fig 11) Find the voltage across the 8 ohm resistor. A. 8v B. 24v C. 20.4v

B. 24v

What is the operating resistance of a 30w light bulb designed for a 28v system? A. 1.07 ohms B. 26 ohms C. 0.93 ohms

B. 26 ohms

Fig 11) Find the total current flowing in the wire between points C and D. A. 2.4a B. 3.0a C. 6.0a

B. 3.0a Rt = R1 x R2/R1 + r2 = 10x40 / 10+40 = 400/50 = 8ohm I-E/R = 24/8 = 3a

A 48v source is required to furnish 192 w to a parallel circuit consisting of three resistors of equal value. What is the value of each resistor? A. 12 ohm B. 36 ohm C. 4 ohm

B. 36 ohm Rt=e^2/p = 48^2/192 = 2304/192 = 12ohm Rt x N = 12 x 3 = 36 ohm

In a parallel circuit with three 6 ohm resistors across a 12v battery, what is the total current (it) value in the circuit? A. 12a B. 6a C. 2a

B. 6a Voltage across branches It=i1+i2+i3 I=e/r = 12/6 =2 I = 12/2 =6

Which requires the most electrical power? (Note: 1 HP = 746w) A. Four 30w lamps arranged in a 12v parallel circuit B. A 1/5 hp, 24v motor which is 75 percent efficient C. A 24v anticollision light circuit consisting of two light assemblies which require 3 amperes each during operation

B. A 1/5 hp, 24v motor which is 75 percent efficient a = 30+30+30+30 = 120w b= 746x1/5 = 149.2/.75 = 198.93w c= p=a(i) x voltage(e) = p=6x24=144w

A 14 ohm resistor is to be installed in a series circuit carrying .05 ampere. How much power will the resistor be required to dissipate? A. At least .70 milliwatt B. At least 35 milliwatts C. Less than .035 milliwa

B. At least 35 milliwatts P= a^2 x r = .05a^2 x 14 = .0025a x 14 = .035w 1000 milliwatt = 1 watt = 35 milliwatts

Nickel-cadmium batteries which are stored for a long period of time will show a low liquid level because A. of current leakage from individual cells B. electrolyte becomes absorbed into the plates C. electrolyte evaporates through the vents

B. Electrolyte becomes absorbed into the plates.

When inductors are connected in series in a circuit, the total inductance is (where the magnetic fields of each inductor do not affect the others) (Note: Lt = L1+L2+L3...) A. Equal to the inductance of the highest rated inductor B. Equal to the sum of the individual inductances C. Less than the inductance of the lowest rated inductor.

B. Equal to the sum of the individual inductances.

What may result if water is added to a nickel-cadmium battery when it is not fully charged? A. Excessive electrolyte dilution B. Excessive spewing is likely to occur during the charging cycle C. No adverse effects since water may be added anytime

B. Excessive spewing is likely to occur during the charging cycle.

Which condition is an indication of improperly torqued call link connections of a nickel-cadmium battery? A. Light spewing at cell caps B. Heat or burn marks on the hardware C. Toxic and corrosive deposits of potassium carbonate crystals

B. Heat or burn marks on the hardware.

Through which material will magnetic lines of force pass the most readily? A. Copper B. Iron C. Aluminum

B. Iron

Through which material will magnetic lines of force pass the most readily? A. Copper B. Iron C. Aluminum

B. Iron.

(Fig 3) When more than two inductors of different inductances are connected in parallel in a circuit, the total inductance is A. Equal to the inductance of the highest rated inductor B. Less than the inductance of the lowest rated inductor C. Equal to the sum of the individual inductances

B. Less than the inductance of the lowest rated inductor

Which of the following best describes the contributing factors to thermal runaway in a Ni-Cad battery installed in an aircraft? A. Low internal resistance intensified by high cell temperatures and a high voltage discharge/charge rate in a constant current charging system. B. Low internal resistance intensified by a high cell temperatures and a high current discharge/charge rate in a constant potential (voltage) charging system. C. High internal resistance intensified by high cell temperatures and a high current discharge/charge rate in a constant potential (voltage) charging system.

B. Low internal resistance intensified by high cell temperatures and a high current discharge/charge rate in a constant potential (voltage) charging system.

Which term means .001 ampere? A. Kiloampere B. Milliampere C. Microampere

B. Milliampere Milli (10 to the -3) - one thousandth of

he presence of any small amount of potassium carbonate deposits on the top of ni-cad battery cells in a service is an indication of A. Plate sulfation B. Normal operation C. Excessive gassing

B. Normal operation

The voltage drop in a circuit of known resistance is dependent on A. The voltage of the circuit B. The amperage of the circuit C. Only the resistance of the conductor and does not change with a change in either voltage or amperage.

B. The amperage of the circuit.

A 1-horsepower, 24v DC electric motor that is 80 percent efficient requires 932.5 w. How much power will a 1-horsepower, 12v DC electric motor that is 75 percent efficient require? (Note: 1hp = 746 w) A. 994.6w B. 932.5w C. 1,305.5w

. 994.6w 746 = 100% efficient = 746w Divide output by efficiency = 746w/.75 = 994.6w

A lead-acid battery with 12 cells connected in series (no-load voltage=2.1v per cell) furnishes 10a to a load of 2ohm resistance. The internal resistance of the battery in this instance is A. 0.52a B. 5.0a C. 2.52a

A. 0.52a 12x2.1 - 25.2v10a to 2ohm = 10x2 = 20v 25.2v-20v= 5.2v5.2/10 = 0.52a

(Fig 21) Which symbol represents a variable resistor? A. 2 B. 1 C. 3

A. 2 (Resistor with arrow going through it at 45 degree angle)

(Fig 4) How much power is being furnished to the circuit? A. 2,645w B. 2,875w C. 575w

A. 2,645w P=i^2 x r = 23^2 x 5 = 2,645w

.002KV equals A. 2.0 v B. .2 v C. 20v

A. 2.0v Take .002 and move decimal 3 to the right for kilo

How much power must a 24v generator furnish to a system which contains the following loads? (Note: 1 HP = 746w)1 Motor (75% efficient) 1/5 HP3 Position Lights 20w each1 Heating element 5amp1 Anticollision light 3amp A. 450 W B. 402 W C. 385 W

A. 450 W 1 Motor = 746x.2 / .75 = 199w 3 Position Lights = 3x20 = 60w each 1 Heater = 5a x 24v = 120w 1 Anti-collision light = 3a x 24v = 72w 199+60+120+72= 451 = 450 total

Nickel-Cadmium battery cases and drain surfaces which have been affected by electrolyte should be neutralized with a solution of A. Boric acid B. Sodium bicarbonate C. Potassium hydroxide

A. Boric acid

In a nickel-cadmium batteries, a rise in cell temperature A. Causes a decrease in internal resistance B. Causes an increase in internal resistance C. Increases cell voltage

A. Causes a decrease in internal resistance.

The end-of-charge voltage of a 19-cell ni-cad battery, measured while still on charge A. Depends upon its temperature and method used for charging B. Must be 1.4v per cell C. Must be 1.2 to 1.3 volts per cell

A. Depends upon its temperature and method used for charging.

Unless other wise specified, any values given for current or voltage in an AC circuit are assumed to be A. Effective values B. Instantaneous values C. Maximum values

A. Effective values

The basis for transformer operation in the use of alternating current is mutual. A. Inductance B. Reactance C. Capacitance

A. Inductance

(Fig 1) When different rated capacitators are connected in series in a circuit the total capacitance is A. Less than the capacitance of the lowest rated capacitor B. Equal to the sum of all capacitances C. Greater than the capacitances of the highest rated capacitor.

A. Less than the capacitance of the lowest rated capacitor.

What determines the amount of current which will flow through a battery while it is being charged by a constant voltage source? A. The total plate area of the battery B. The state-of-charge of the battery C. The ampere-hour capacity of the batter

B. The state-of-charge of the battery

What is the purpose of the ground symbol used in electrical circuit diagram? A. To show that there is common bus for connection of the source of electrical energy to the load B. To show that there is a return path for the current between the source of electrical energy and the load C. To show the source of electrical energy for the load

B. To show that there is a return path for the current between the source of electrical energy and the load.

Which is correct concerning a parallel circuit? A. Total voltage drop is the same as the total resistance B. Total resistance will be smaller than the smallest resistance C. Total resistance will decrease when one of the resistances is removed

B. Total resistance will be smaller than the smallest resistor.

Which is correct concerning a parallel circuit? A. Total voltage drop is the same as the total resistance B. Total resistance will be smaller than the smallest resistance C. Total resistance will decrease when one of the resistances is removed

B. Total resistance will be smaller than the smallest resistor..

(Fig 2) What is the total capacitance of a certain circuit containing three capacitances of .02 micro-farad, .05 micro-farad, and .10 micro-farad respectively? A. 0.125pF B .170uF C. .0125uF

C. .0125uF 1/.02 + 1/.05 + 1/.10 = .0125uF

If three resistors of 3 ohms, 5 ohms, and 22 ohms are connected in series in a 28-volt circuit, how much current will flow through the 3-ohm resistor? A. 1.05a B. 9.3a C. 0.93a

C. 0.93a 3+5+22 = 30 ohm I=e/r = 28/30 = .933

A circuit has an applied voltage of 30v and a load consisting of 10 ohm resistor in a series with a 20 ohm resistor. What is the voltage drop across the 10 ohm resistor? A. 30v B. 20v C. 10v

C. 10v

A 24v source is required to furnish 48w to a parallel circuit consisting of four resistors of equal value. What is the voltage drop across each resistor? A. 6v B. 12v C. 24v

C. 24v

In a parallel circuit with four 6 ohm resistors across a 24v battery, what is the total voltage across resistor-three (VR3) in the circuit? A. 6v B. 18V C. 24v

C. 24v

When different rated capacitors are connected in parallel in a circuit, the total capacitance is (Note: Ct=C1+C2+C3) A. Equal to the capacitance of the highest rated capacitor B. Less than the capacitance of the lowest rated capacitor C. Equal to the sum of all the capacitances.

C. Equal to the sum of all the capacitances.

The term that describes the combined resistive forces in an ac circuit is A.Resistance B. Reactance C. Impedance

C. Impedance

The electrolyte of a nickel-cadmium battery is the lowest when the battery is A. being charged B. under a heavy load condition C. in a discharged condition

C. In a discharged condition.

The correct way to connect a test volt meter in a circuit is A. In series with a unit B. Between the source voltage and the load C. In parallel with a unit

C. In parallel with a unit

An increase in which of the following factors will cause an increase in the inductive reactance of a circuit? A. Resistance and capacitive reactance B. Resistance and voltage C. Inductance and frequency

C. Inductance and frequency.

(Fig 7) If the resistor R(3) is disconnected at terminal D, what will the ohmmeter read? A. 10 ohm B. 20 ohm C. Infinite resistance

C. Infinite resistance

In an AC circuit, the effective voltage is A. Greater than the maximum instantaneous voltage B. Equal to the maximum instantaneous voltage C. Less than the maximum instantaneous voltage

C. Less than the maximum instantaneous voltage

A fully charged lead-acid battery will not freeze util extremely low temperatures are reached because A. increased internal resistance generates sufficient heat to prevent freezing B. the acid is in the plates , thereby increasing the specific gravity of the solution C. most of the acid is in the solution

C. Most of the acid is in the solution

The purpose of providing a space underneath the plates in a lead acid battery's call container is to A. Allow for conventional flow of the electrolyte in order to provide for cooling of the plates B. Ensure that the electrolyte quantity ratio to the number of plates and plate area is adequate C. Prevent sediment buildup from contacting the plates and causing a short circuit

C. Prevent sediment buildup from contacting the plates and causing a short circuit.

Which statement is true regarding the hydrometer reading of a lead-acid storage battery electrolyte s true? A. The hydrometer reading will give a true indication of the capacity of the battery regardless of the electrolyte temperature. B. A specific gravity correction should be added to the hydrometer reading if the electrolyte temperature is below 59 degrees F C. The hydrometer reading does not require a temperature correction if the electrolyte temperature is 80 degrees F

C. The hydrometer reading does not require a temperature correction if the electrolyte temperature is 80 degrees F.

The potential difference between two conductors which are insulated from each other is measured in A. Coulombs B. Amperes C. Volts

C. Volts

What unit is used to express electrical power? A. Ampere B. Volt C. Watt

C. Watt Ampere=current Voltage=pressure Watt=power