AP Physics B multiple choice questions, with answers, similar to the questions in the AP physics exam are presented. The questions are on electric circuits with resistors, capacitors and other electric components where current, voltage power are calculated. The answers are at the bottom of the page.

1. 
   The plates of a parallel plates capacitor are squares of side x and are separated by a distance d. Which of the following statements is true if x and d are doubled? The capacitance is
   
   A) doubled
   B) not changed
   C) quadrupled
   D) halved
   E) multiplied by 3
   

2. 
   What is the intensity of the electric current that flows through resistor $R_4$ when the switch $S_1$ is closed?
   
   A) 0.075 A
   B) 0.05 A
   C) 0.225
   D) 1.5 A
   E) 0.5 A
   

3. 
   What is the intensity of the electric current that flows through resistor $R_4$ when both switches $S_1$ and $S_2$ are closed?
   
   A) 0.075 A
   B) 0.05 A
   C) 0.225
   D) 1.5 A
   E) 0.5 A
   

4. 
   In the circuit below r is the internal resistor of a V-Volt battery. What is the power dissipated by r.
   
   A) \( r\dfrac{V^2}{(1.5R)^2} \)
   
   B) \( \dfrac{V^2}{r} \)
   
   C) \( r\dfrac{V}{r+1.5R} \)
   
   D) \( r\dfrac{V^2}{(r+R)^2} \)
   
   E) \( r\dfrac{V^2}{(r+1.5R)^2} \)
   

5. 
   What is the power dissipated by a resistance of 100 ohms in series with another resistance of 50 ohms and both connected to a battery of 3 Volts with negligible internal resistance?
   
   A) 4000 mW
   B) 0.4 mW
   C) 40 mW
   D) 0.02 mW
   E) 400 mW
   

6. 
   A maximum current flows through resistor R4 is
   
   A) S1 is open, S2 is closed and S3 is closed
   
   B) S1 is closed, S2 is closed and S3 is open
   
   C) S1 is closed, S2 is open and S3 is closed
   
   D) S1 is closed, S2 is open and S3 is open
   
   E) S1 is open, S2 is closed and S3 is closed
   

7. 
   What should be the capacitance X so that the equivalent capacitance of all three capacitor is equal to $\dfrac{11}{3}C$?
   
   A) 3C
   
   B) 0.5C
   
   C) 4C
   
   D) 1.5C
   
   E) 2C
   

8. 
   Which of the following expressions can be used to find the current through resistor 3R in the circuit below?
   
   A) \( \dfrac{V}{3.4R} \)
   
   B) \( \dfrac{V}{7R} \)
   
   C) \( \dfrac{V}{3R} \)
   
   D) \( \dfrac{V}{5R} \)
   
   E) \( \dfrac{V}{6R} \)
   

1. A
2. B
3. A
4. E
5. C
   
6. B
7. E
8. C