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

**A two farad and a four farad capacitor are connected in series. What single capacitance is "equivalent" to this combination?**

**ANSWER**: 4/3 FARADS

**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

**ANSWER**: W – CONSTANT

**A 10 farad capacitor is used in a circuit. The voltage difference between the plates of the capacitor is 20 volts. What is the magnitude of the charge on each of the capacitor's plates?**

**ANSWER**: 200 COULOMBS

**A circuit which employs a DIRECT CURRENT source has a branch which contains a capacitor. After the circuit has reached a steady state, what is the magnitude of the current in the circuit branch which contains the capacitor?**

**ANSWER**: THE CURRENT IS ZERO

**A charged particle is moving in a UNIFORM magnetic field. If the direction of motion of the charged particle is parallel to the magnetic field, describe the shape of the charged particle's path.**

**ANSWER**: STRAIGHT LINE

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

w) points radially away from the wire

x) points radially inward

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.

x) pointing radially outward

y) pointing radially inward

z) circles the axis of the rod

**ANSWER**: Z -- CIRCLES THE AXIS OF THE ROD

**Iron is what type of magnetic material? Is it:**

w) diamagnetic

x) paramagnetic

y) ferromagnetic

z) non-magnetic

**ANSWER**: Y -- FERROMAGNETIC