Question 1

Which of the following statements about the relationship between electric field ($$\vec{E}) $$and electric potential ($$V) is $$correct?

Accepted Answer

$$\vec{E} is $$perpendicular to equipotential surfaces and points in the direction of decreasing $$V.$$

Question 2

A parallel-plate capacitor is disconnected from a battery after being charged. If the plates are then pulled farther apart, what happens to the charge $$Q on $$the plates and the potential difference $$\Delta V_C$$ between them?

Accepted Answer

$$Q$$ stays constant, $$\Delta V_C$$ increases.

Question 3

Which equation correctly expresses the capacitance $$C of a $$parallel-plate capacitor with plate area $$A$$, plate separation $$d$$, and dielectric constant $$\kappa$$?

Accepted Answer

$$C = \kappa \$$epsilon_0$$ \dfrac{A}{d}$$

Question 4

A camera flash capacitor stores $$10\ \mathrm{J} of $$energy at $$300\ \mathrm{V}. To $$store $$90\ \mathrm{J} in $$the same capacitor, what potential difference is required?

Accepted Answer

$$900\ \mathrm{V}$$

Question 5

Which of the following best describes the function of a dielectric in a capacitor?

Accepted Answer

It increases the capacitance by decreasing the electric field.

Question 6

A cell membrane can be modeled as a parallel-plate capacitor. If the membrane thickness $$d is $$halved while the area $$A$$ and dielectric constant $$\kappa$$ remain the same, what happens to the capacitance?

Accepted Answer

It is doubled.

Question 7

The Nernst potential for an ion across a cell membrane is given by $$\Delta V = \dfrac{k_B T}{e} \ln \dfrac{c_{out}}{c_{in}}. If$$ $$c_{out}$$ increases while $$c_{in}$$ remains constant, what happens to $$\Delta V$$?

Accepted Answer

$$\Delta V$$ increases.

Question 8

Which of the following is true for the sum of all potential differences around a closed loop in a circuit?

Accepted Answer

It is zero.

Question 9

A wire carries a current $$I to $$the right. What is the direction of the magnetic field directly above the wire?

Accepted Answer

Into the page

Question 10

A charged particle with charge $$q$$ and mass $$m$$ moves perpendicular to a uniform magnetic field $$B at $$speed $$v. $$What is the radius of its circular path?

Accepted Answer

$$r = \dfrac{mv}{qB}$$

Question 11

In a simple RC circuit, the time constant $$	au is $$given by:

Accepted Answer

$$	au = RC$$

Question 12

Which of the following best describes the current in a charging RC circuit immediately after the switch is closed?

Accepted Answer

It is at its maximum value.

Question 13

A resistor of resistance $$R$$ and a capacitor of capacitance $$C$$ are connected in series to a battery of emf $$\mathcal{E}. $$What is the charge on the capacitor after a very long time?

Accepted Answer

$$Q = \mathcal{E}C$$

Question 14

Which of the following is true about the current through resistors in series?

Accepted Answer

The current is the same through all resistors.

Question 15

If three identical resistors are connected in parallel to a battery, what happens to the total current compared to a single resistor connected to the same battery?

Accepted Answer

The total current is three times as much.

Question 16

A solenoid has $$N$$ turns, length $$L$$, and carries current $$I. $$What is the magnetic field inside the solenoid?

Accepted Answer

$$B = \mu_0$ \dfrac{N}{L} I$$

Question 17

A current-carrying loop is placed in a uniform magnetic field. What happens to the loop?

Accepted Answer

It experiences a torque that tends to align its magnetic dipole moment with the field.

Question 18

Which of the following best describes the direction of the magnetic force on a positive charge moving in a magnetic field?

Accepted Answer

Perpendicular to both the velocity and the magnetic field.

Question 19

Two long, parallel wires carry currents in the same direction. What is the nature of the force between them?

Accepted Answer

They attract each other.

Question 20

A mass spectrometer separates ions based on their mass-to-charge ratio. If two ions have the same charge but different masses, how will their paths differ in a uniform magnetic field?

Accepted Answer

The ion with greater mass will have a larger radius of curvature.

Electric Potential, Capacitance, and Circuits: Study Notes for Physics 202

Study Guide - Practice Questions

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