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 patient is undergoing an electrocardiogram (ECG). What physical principle allows the ECG to detect the heart's electrical activity?

Accepted Answer

The heart acts as a moving electric dipole, creating time-varying potential differences across the body.

Question 3

For a parallel-plate capacitor with plate area $$A$$ and separation $$d$$, what is the correct formula for its capacitance $$C in $$vacuum?

Accepted Answer

$$C = \$$epsilon_0$$ \frac{A}{d}$$

Question 4

A capacitor is charged to a potential difference $$\Delta V_C$$ and then disconnected from the battery. If the plate separation is increased, what happens to the charge $$Q$$ and the potential difference $$\Delta V_C$$?

Accepted Answer

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

Question 5

Which of the following best describes the energy stored in a capacitor?

Accepted Answer

$$U_C = \frac{1}{2} C \Delta V_C^2$

Question 6

A dielectric with dielectric constant $$\kappa is $$inserted between the plates of a capacitor connected to a battery. What happens to the charge $$Q$$ and the potential difference $$\Delta V_C$$ across the capacitor?

Accepted Answer

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

Question 7

The Nernst potential for an ion across a cell membrane is given by $$\Delta V = \frac{k_B T}{e} \ln \frac{c_{out}}{c_{in}}. If$$ $$c_{out} \u003e c_{in}$$, what is the sign of $$\Delta V$$?

Accepted Answer

Positive

Question 8

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 9

A charged particle with charge $$q$$ and velocity $$\vec{v}$$ enters a region with a uniform magnetic field $$\vec{B}$$ perpendicular to $$\vec{v}. $$What is the radius of the particle's circular path?

Accepted Answer

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

Question 10

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

Accepted Answer

$$	au = RC$$

Question 11

A resistor of $$10\ \Omega$$ and a resistor of $$20\ \Omega$$ are connected in parallel. What is the equivalent resistance?

Accepted Answer

$$6.67\ \Omega$$

Question 12

Which of the following is true for resistors connected in series?

Accepted Answer

The total resistance is the sum of the individual resistances.

Question 13

A current of $$2\ \mathrm{A}$$ flows into a junction, and two wires carry currents of $$1\ \mathrm{A}$$ and $$0.5\ \mathrm{A}$$ out of the junction. What is the magnitude and direction of the unknown current in the fourth wire?

Accepted Answer

$$0.5\ \mathrm{A}$$ out

Question 14

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

Accepted Answer

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

Question 15

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

Accepted Answer

$$900\ \mathrm{V}$$

Question 16

Which of the following best describes the direction of the force on a negative charge in an electric field?

Accepted Answer

Opposite to the electric field direction

Question 17

In a closed loop, the sum of all potential differences is:

Accepted Answer

$$\sum \Delta V = 0$$

Question 18

A charged particle moves with velocity $$\vec{v}$$ perpendicular to a uniform magnetic field $$\vec{B}. $$What is the direction of the magnetic force on a positive charge?

Accepted Answer

Perpendicular to both $$\vec{v}$$ and $$\vec{B}$$, given by the right-hand rule

Question 19

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.

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

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