Standardized Test Prep
Test-Taking Tip
When a question refers to a diagram, start by scanning the whole diagram. See if you can remember what each symbol means.
In a circuit diagram, determine if the circuit is series or parallel. Check to make sure that each part of the circuit is complete. In the question below, a wire goes to device #2, but no wire leaves it, so no current enters the device.
The direction of current is from the positive terminal to the negative terminal of the voltage source. Note that the direction of current is opposite the direction of electron flow. In the circuit below, current is in a clockwise direction.
In what order does current flow in the circuit above?
5 − 6 − 7 − 1 − 5 − 3 − 4
6 − 7 − 8 − 2 − 5 − 1 − 3 − 4
4 − 3 − 5 − 7 − 6
3 − 2 − 5 − 6 − 4 − 7
4 − 3 − 1 − 5 − 8 − 7 − 6
(Answer: E)
In the diagram above, the battery is replaced by an AC voltage source. Which of the following is now true?
The current enters and leaves device #2.
The current is always clockwise.
There is not net movement of charge in the circuit.
The current is always counterclockwise.
There is no current in the circuit.
If you rub a neutral glass rod with silk, the silk acquires a negative charge. If you rub a neutral glass rod with a rubber rod, the rubber acquires a negative charge. If you rub a neutral rubber rod with silk, the rubber rod acquires a negative charge. Which of the three materials has the strongest attraction for electrons?
glass
silk
rubber
not enough data to answer
none, because they have equal attractions for electrons
A 1.5-m wire carries a 5.0-A current when a potential difference of 3.7 V is applied. What is the resistance of the wire?
0.49 ohms
0.74 ohms
1.1 ohms
1.4 ohms
2.0 ohms
A space heater is connected to a standard 120-V line. If the resistance of the operating heater is 15 ohms, what power does the heater use? (Hint: First calculate the current.)
8.0 W
64 W
960 W
1800 W
220 kW
A 1700-W machine operates at 120 V. What is the resistance in the machine?
1.4 ohms
8.5 ohms
14 ohms
A lamp with three 40-W bulbs connected in parallel is plugged into a 120-V outlet. What is the current in the lamp?
1 A
3 A
9 A
40 A
120 A