Physics Chapter 13
What is meant by a short circuit?
A short circuit is offering path of a very low resistance. It creates a large current.
TRUE or FALSE A series circuit contains branching points and multiple paths for current to flow through.
False
There is only one path for current.
Series
Which of the following is TRUE about alternating current? a. Alternating current flows in one direction only b. Batteries run on alternating current c. The electricity in your home uses alternating current d. Alternating current is easy to recharge
c
Which of the following is TRUE about voltage in a series circuit? The total of all voltage drops must: a. Equal the total current b. Add up to zero c. Add up to the total voltage supplied by the battery. d. Never exceed the total circuit resistance.
c
A short circuit can be dangerous when excessive _______________ cause wires to heat up a. Voltage b. Resistance c. Capacitance d. Current
d
A student connects THREE 1-ohm light bulbs to a 9-volt battery in parallel. The total current is_________ amperes a. 1 b. 3 c. 9 d. 27
d
Electric energy is measured in a. Ohms b. Watts c. Electron-hours d. Kilowatt-hours
d
Kirchoff's law applies to a parallel circuit because it states that: a. Current is the same everywhere throughout one entire circuit b. Current is the same everywhere throughout branching circuit paths c. Current stays the same as more branches are added to a parallel circuit d. All the current flowing into a branch point must flow out again.
d
The power used by a circuit can be found by: a. Using Ohm's law b. Dividing voltage by current c. Adding all resistances
d
What happens to a circuit's resistance as more resistors are added in series?
As more bulbs are added, the total resistance in a circuit increases and the brightness of the bulbs decreases.
What is a difference between direct current and alternating current?
Direct current is the electric current that flows in one direction only. Alternating current is the electric current that reverses its direction at REGULAR INTERVALS.
TRUE or FALSE A fuse or circuit breaker used in a circuit is usually inserted in parallel.
False
TRUE or FALSE A kilowatt-hour (kWh) is a unit of power.
False
Give an example of a circuit that uses alternating current and an example of a circuit that uses direct current.
Flashlights - DC; Household Appliances- AC - Most of them
The voltage across each branch is the same and is equal to the battery voltage.
Parallel
There are multiple paths for current.
Parallel
Suppose you have purchased a string of lights. You want to find out if the lights are wired in series or in parallel. How could you quickly determine how the lights have been wired?
Remove one bulb from the string of lights while current is running through the string. If remaining bulbs go out, the string is wired in series. If the remaining bulbs remain lighted, the string is wired in parallel
Current is the same at every point in the circuit.
Series
Total battery voltage is equal to the sum of the voltages across each resistor.
Series
Distinguish between a series circuit and a parallel circuit.
Series -single path for current; parallel- alternate paths
What happens to the total current in a parallel circuit as more branches are added? Why?
The total current in a parallel circuit increases as more branches are added. The total current is the sum of the currents in each branch. The only time branches have an effect on each other is when the total current is more than the battery or wall outlet can supply.
What is a function of a fuse or circuit breaker in a circuit?
To stop dangerously high current.
TRUE or FALSE Each branch of a parallel circuit has the same voltage.
True
TRUE or FALSE Electric power is a measure of the rate at which electricity does work.
True
TRUE or FALSE In a series circuit, the total voltage drop across a series of resistors is the sum of voltage drops across each individual resistor.
True
TRUE or FALSE Kirchhoff's current law states that all the current entering a branch point must exit the point.
True
TRUE or FALSE The current from battery is always direct current (DC).
True
TRUE or FALSE The total amount of electric energy used depends on the total power used and the total time of use.
True
A 60-W light bulb and a 100-W light bulb are each connected to a 120-V outlet. Which light bulb has more current in it? a. the 60-W bulb b. the 100-W bulb c. the same amount of current flows in both
a
A circuit containing two identical branches has a. One-half the resistance it would have if it only contained one of the branches b. Twice the resistance it would have if it only contained one of the branches. c. The same resistance it would have if it only contained one of the branches d. No resistance at all.
a
As more lamps are put into a parallel circuit, the overall current in the circuit a. increases b. stays the same c. decreases
a
Compared to the resistance of two resistor connected in series, the same resistors connected in parallel have a. less resistance b. more resistance c. the same resistance
a
Electric power is defined as: a. Current times voltage b. Current divided by voltage c. Current times resistance d. Voltage divided by current
a
If there is a break at any point in a series circuit, the current will: a. Stop everywhere in the circuit b. Leak out of the break point c. Be decreased by one-half d. Continue through remaining unbroken circuit branches.
a
If you plug an electric toaster rated at 110-V into a 220-V outlet, current in the toaster will be a. Twice what it should be b. The same as if it were plugged into 110 V c. Half what it should be d. More than twice what it should be
a
The wiring in your home uses ______________circuits. a. Parallel b. Series c. Two-way d. Three-way
a
When a new branch containing a resistor is added to a parallel circuit, the total resistance: a. Decreases b. Increases c. Stays the same d. May increases or decrease, depending on the device.
a
Which of the following would create a total resistance of 0.5 ohm? a. Four 2-ohm resistors connected in parallel b. Four 2-ohm resistors connected in series c. Eight 2-ohm resistors connected in parallel d. Two 2-ohm resistors connected in series
a
A 120-watt light bulb is connected to a 120-V outlet. How much current is in the light bulb? a. 0.5 A b. 1 A c. 2 A d. 6 A
b
A 75-watt light bulb uses 75: a. Joules of energy until it burns out b. Joules of energy every second c. Joules of energy every hour d. 75 watts of power every hour
b
A flashlight contains a 12 W bulb that uses 2 A of current. How many 1.5 -V batteries does it use a. 2 b. 4 c. 6 d. 8
b
How much power is used by a 12- V car battery that draws 0.5 A of current? a. 0.5 W b. 6 W c. 12 W d. 24 W
b
Power outlets in our homes typically have a potential difference of a. 30V b. 120 V c. 60 V d. 120 A
b
The current in a series circuit: a. Decreases to zero as it travels through the circuit b. Is the same at all points in a circuit c. Is greatest in the resistor with the highest resistance d. Is greatest in the resistor with the lowest resistance
b
When more devices are added to a series circuit, the total circuit resistance: a. Decreases b. Increases c. Stays the same d. May increase or decrease, depending on the device
b
When resistors are put in series next to each other, their overall resistance is a. The same as the resistance of one of the resistors b. Larger than the resistance of any individual resistor c. Smaller than the resistance of any of the resistors.
b
When two light bulbs are connected in series, the a. Current through each light bulb is proportional to the resistance of the bulb. b. Same amount of current always flows through each bulb c. Neither A nor B
b
A light bulb is plugged into a 120-V outlet and has a 0.7 a current in it.. What is the power rating of the light bulb? a. 12 W b. 17 W c. 84 W d. 120 W
c
A stereo uses 3 A of current when plugged into a 120-V outlet. What is its power? a. 120 W b. 240 W c. 360 W d. 60 W
c
An electric heater is rated at 300 W for use in a 110-V circuit. The circuit breaker in the circuit can handle 12 A of current. How many heaters can be safely operated in the circuit? a. 2 b. 3 c. 4 d. 5
c
As more lamps are put into a series circuit, the overall current in the circuit a. Stays the same b. Increases c. decreases
c
How much current is used by a- 3,600 W electric oven operating on a 120 V circuit? a. 2 A b. 3 A c. 30A d. 300 A
c
The watt is a unit that represents the: a. Resistance of a wire to current flowing through it. b. Flow of charge in a circuit c. Rate at which energy is changed from one form to another d. Potential energy difference between two places in a circuit.
c
There are different paths for an electric current to take in a(an) a. Series circuit b. Open circuit c. Parallel circuit d. Closed circuit
c
What is the basic difference between series and parallel circuits? a. Simple series circuits are not used in electrical devices; parallel circuits are used in all electrical devices b. In series circuit, there are multiple paths for the flow of charge; in parallel circuit, there are only two paths c. A series circuit contains one path for the flow of charge; a parallel circuit contains more than one path d. A series circuit obeys Ohm's law; a parallel circuit does not obey Ohm's law
c
When one light bulb in a parallel circuit containing several light bulbs burns out, the other light bulbs a. do not burn at all b. burn brighter c. burn the same as before
c
Which of the following devices draws the most current when operating on a 120-volt circuit? a. 10-watt clock radio b. 40-watt light bulb c. 50-watts fun
c
What do we buy from the electric utility company? a. Power, in watts b. Energy, in kilowatt-hours c. Current, in amperes d. Voltage in volts
d
When electrons move back and forth reversing their direction regularly, the current is called a. Direct current b. Series current c. Electric charge d. Alternating current.
d
When plugged into a 120-V wall outlet, how much current is used by an electric blanket rated at 140 W? a. 16,800 A b. 140 A c. 120 A d. 1.2 A
d
Which of the following is correct relationship among power, current, and voltage? a. P=I/V b. V= P x I c. Ω = P x I d. P = V x I
d
TRUE or FALSE In a parallel circuit, current in each branch is the same.
false
TRUE or FALSE When light bulbs are connected in series, all carry the same current regardless of their resistances.
true
TRUE or FALSE When resistors are arranged in parallel, their overall resistance is less than that of the smallest resistor.
true