Question 1

Which of the following statements about electric current is INCORRECT?

Accepted Answer

In most electric circuits, electrons move in the same direction as the electric current.

Question 2

A wire resistor has resistivity $$\rho$$, length $$L$$, and cross-sectional area $$A. $$Which of the following is TRUE?

Accepted Answer

None of the above statements is true.

Question 3

Two identical batteries with emf $$\mathcal{E}$$ are connected in series with a single resistor $$R. If$$ $$V = 0\ \mathrm{V} is $$defined at the negative terminal of the lower battery, what is the correct ranking of the electric potentials $$V_A, V_B, V_C, V_D, V_E$$ from highest to lowest, assuming ideal wires?

Accepted Answer

$$V_A \u003e V_B = V_C \u003e V_D = V_E$$

Question 4

A conductor's current vs. potential difference graph shows a straight line up to $$\Delta V = V'$$, then curves. Which statement is correct?

Accepted Answer

The resistance below $$\Delta V = V' is $$given by the slope of the straight-line segment.

Question 5

A cylindrical wire resistor with radius $$R$$ and length $$L is $$connected to a battery with emf $$\mathcal{E}$$, generating heat. If both the radius and length are doubled, which statement is correct?

Accepted Answer

Neither of them is true.

Question 6

In the circuit shown, which statement is NOT true?

Accepted Answer

Resistor $$R_1 is $$connected to the combined resistor $$R_2$$-$$R_3 in $$parallel.

Question 7

A resistor $$R$$ and a capacitor $$C$$ are connected in series to a battery of voltage $$V. $$The switch is closed at $$t=0. $$The charge stored in the capacitor as a function of time is $$Q(t) = CV(1 - e$$^{-t/	au}$$). $$Which statement is true?

Accepted Answer

None of the above statements is true.

Question 8

Given the following equations for a circuit with $$R_1$$ = $$R_2$$ = $$R_3 = 100$$\ \Omega$$:

$$\begin{align*}
(1)\quad & $$I_1$$ - $$I_2$$ - $$I_3 = 0$$ \
(2)\quad & 15\mathrm{V} - $$I_2$$ 	imes 100\Omega - $$I_1$$ 	imes 100\Omega = 0 \
(3)\quad & 15\mathrm{V} - 9\mathrm{V} - $$I_3$$ 	imes 100\Omega - $$I_1$$ 	imes 100\Omega = 0
\end{align*}$$

If $$($$I_1$$, $$I_2$$, $$I_3) = (0.07$$\ \mathrm{A}, 0.08\ \mathrm{A}, -0.01\ \mathrm{A})$$, which statement is NOT true?

Accepted Answer

The electric potential difference across $$R_2 is $$the same as that across $$R_3.$$

Question 9

Three particles travel through a region where the magnetic field is out of the page. Their paths curve differently. What are the signs of the charges of these three particles?

Accepted Answer

1 is neutral, 2 is negative, and 3 is positive.

Question 10

A wire is placed between the poles of a horseshoe magnet (left is north, right is south). When the switch is closed, which way will the wire initially deflect?

Accepted Answer

Downward

Question 11

A charged particle moves in a static uniform magnetic field. Which statement is correct?

Accepted Answer

The particle may experience a magnetic force, but its speed will not change.

Question 12

If you cut a straight bar magnet in half (with the south pole on the left and the north pole on the right), what will be the magnetic poles of the left piece?

Accepted Answer

The left piece will have a south pole on its left end and a north pole on its right end.

Question 13

Kirchhoff’s junction rule follows from which physical law?

Accepted Answer

Conservation of charge

Question 14

If capacitors are connected in parallel to a battery, which statement is correct?

Accepted Answer

They all have the same voltage across them.

Question 15

An electron moves through a region of uniform magnetic field. Which statement is correct?

Accepted Answer

The electron's speed remains constant if only the magnetic force acts.

Question 16

A real-world application: In MRI machines, strong uniform magnetic fields are used. If a proton moves perpendicular to the field, what is the nature of its path and kinetic energy?

Accepted Answer

The proton moves in a circle and its kinetic energy remains constant.

Question 17

A household circuit contains a fuse rated at 10 A. If three appliances are connected in parallel, each drawing 4 A, what will happen?

Accepted Answer

The fuse will blow because the total current exceeds 10 A.

Question 18

A capacitor of $$2\ \mu\mathrm{F}$$ and a resistor of $$1\ \mathrm{k}\Omega$$ are connected in series to a $$12\ \mathrm{V}$$ battery. How long does it take for the capacitor to reach approximately 63% of its maximum charge?

Accepted Answer

$$1\ \mathrm{ms}$$

Question 19

A wire of length $$L$$ and radius $$r$$ has resistance $$R. If $$the wire is stretched to double its original length without changing its volume, what happens to its resistance?

Accepted Answer

The resistance increases by a factor of 4.

Question 20

A patient receives a defibrillator shock using two paddles. If the paddles are modeled as parallel plates with a capacitor of $$100\ \mu\mathrm{F}$$ charged to $$2000\ \mathrm{V}$$, how much energy is delivered to the patient?

Accepted Answer

$$400\ \mathrm{J}$$

PHYS 113 Review: Electric Current, Circuits, Magnetism, and Capacitors

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