Electric Current AP Physics 2 MCQ – Exam Style Questions etc.
Electric Current AP Physics 2 MCQ
Unit 11: Electric Circuits
Weightage : 15–18%
Exam Style Practice Questions , Electric Current AP Physics 2 MCQ
Question
A circuit contains three identical light bulbs and a switch S connected to an ideal battery of\( emf \varepsilon \), as shown in the figure above. The switch is initially open and bulbs A and B have equal brightness, while C is not lit. What happens to the brightness of bulbs A and B when the switch S is closed and bulb C lights up?
Bulb A Bulb B
(A) Remains the same Becomes dimmer
(B) Becomes dimmer Becomes dimmer
(C) Becomes brighter Becomes dimmer
(D) Becomes brighter Not lit
(E) Remains the same Not lit
Answer/Explanation
Ans:C
Questions
Two resistors of resistances R and \(12 \Omega\) are connected to a battery of emf 18 V, as shown in the figure above. The battery has an internal resistance of r. The current in the battery is 1.5 A, and the current in the \(12 \Omega\) resistor is 1.0 A.
What is the resistance R ?
(A) 7.2 \(\Omega\)
(B) 12 \(\Omega\)
(C) 18\(\Omega\)
(D) 24 \(\Omega\)
(E) 45 \(\Omega\)
Answer/Explanation
Ans:D The parallel branches must all have the same voltage, and the current flowing through R must be 0.5A. Therefore,
Eqn1 : 18V -(1.5A)r ( 1.0A )(12Ω)
Eqn2 : 18V-( 1.5A)r ( 0.5A)R
Eqn1- Eqn2: 0 = (1.0A)(122) – (0.5A)R
\( R=\frac{(1.0A)(12\Omega )}{(0.5A)}\)
\( R=24\Omega\)