# PHYS-91(part 2): Multiple Choices and Short Answer question

## Three capacitors with different capacitances are connected in series. Which of the following statements is TRUE?

w) All three of the capacitors have the same potential difference between their plates.

x) The magnitude of the charge is the same on all of the capacitor plates.

y) The capacitance of the system depends on the voltage applied across the three capacitors.

ANSWER: X -- THE MAGNITUDE OF THE CHARGE IS THE SAME ON ALL OF THE CAPACITOR PLATES

## For a parallel-plate capacitor with plate area "A" and plate separation "d", the capacitance is proportional to which of the following?

w) A divided by d squared

x) A times d

y) A divided by d

z) d divided by A

ANSWER: Y -- A DIVIDED BY D

## A constant potential difference is applied across the plates of a parallel-plate capacitor. Neglecting any edge effects, the electric field inside the capacitor is:

w) constant

x) varying as one over r squared

y) decreasing as one moves from the positive to the negative plate z) zero

## An infinitely long wire carries a current of three amps. The magnetic field outside the wire:

w) points radially away from the wire

y) circles the wire

z) is zero.

ANSWER: Y -- CIRCLES THE WIRE

## A copper rod which is 1 centimeter in diameter carries a current of 5 amps. The current is distributed uniformly throughout the rod. The magnetic field half way between the axis of the rod and its outside edge is:

w) zero.

z) circles the axis of the rod

ANSWER: Z -- CIRCLES THE AXIS OF THE ROD

w) diamagnetic

x) paramagnetic

y) ferromagnetic

z) non-magnetic