SAT Physics Practice Test: Direct Current Circuits

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Question 8 questions

Time 6 minutes

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1. A wire made of brass and a wire made of silver have the same length, but the diameter of the brass wire is 4 times the diameter of the silver wire. The resistivity of brass is 5 times greater than the resistivity of silver. If RB denotes the resistance of the brass wire and RS denotes the resistance of the silver wire, which of the following is true?

A. RB = RS
B. RB = RS
C. RB = RS
D. RB = RS
E. RB = RS

2. For an ohmic conductor, doubling the voltage without changing the resistance will cause the current to

A. decrease by a factor of 4
B. decrease by a factor of 2
C. remain unchanged
D. increase by a factor of 2
E. increase by a factor of 4

3. If a 60-watt lightbulb operates at a voltage of 120 V, what is the resistance of the bulb?

A. 2Ω
B. 30Ω
C. 240Ω
D. 720Ω
E. 7,200Ω

4. A battery whose emf is 40 V has an internal resistance of 5 Ω. If this battery is connected to a 15 Ω resistor R, what will be the voltage drop across R ?

A. 10 V
B. 30 V
C. 40 V
D. 50 V
E. 70 V


Determine the equivalent resistance between points a and b.

A. 0.167 Ω
B. 0.25 Ω
C. 0.333 Ω
D. 1.5 Ω
E. 2.0 Ω


Three identical light bulbs are connected to a source of emf, as shown in the diagram above. What will happen if the middle bulb burns out?

A. All the bulbs will go out.
B. The light intensity of the other two bulbs will decrease (but they won’t go out).
C. The light intensity of the other two bulbs will increase.
D. The light intensity of the other two bulbs will remain the same.
E. More current will be drawn from the source of emf.

7. How much energy is dissipated as heat in 20 s by a 100 Ω resistor that carries a current of 0.5 A ?

A. 50 J
B. 100 J
C. 250 J
D. 500 J
E. 1,000 J

8. Two resistors, A and B, are in series in a circuit that carries a nonzero current. If the resistance of Resistor A is 4 times greater than the resistance of Resistor B, which of the following correctly compares the currents through these resistors (IA and IB, respectively) and the voltage drops across them (VA and VB, respectively)?

A. IA = IB and VA = VB
B. IA = IB and VA = 4VB
C. IA = IB and VB = 4VA
D. IA = 4IB and VA = 4VB
E. IB = 4IA and VB = 4VA