Q: In the RC circuit shown, what is the expression for the current $$I(t) as a $$function of time after the switch is closed at $$t=0$$?

$$I(t) = \frac{\text{emf}}{R} e$$^{-t/RC}$$

Q: Which of the following best describes the behavior of the charge $$Q(t) on $$the capacitor in an RC circuit as time increases?

$$Q(t)$$ increases and asymptotically approaches $$C \cdot \text{emf}.$$

Q: What is the Lorentz force acting on a particle with charge $$q$$ moving with velocity $$\vec{v} in $$both electric field $$\vec{E}$$ and magnetic field $$\vec{B}$$?

$$\vec{F} = q\vec{E} + q\vec{v} \times \vec{B}$$

Question 1

In the RC circuit shown, what is the expression for the current $$I(t) as a $$function of time after the switch is closed at $$t=0$$?

Accepted Answer

$$I(t) = \frac{	ext{emf}}{R} e$$^{-t/RC}$$

Question 2

What is the physical meaning of the time constant $$	au = RC in an RC $$circuit?

Accepted Answer

It is the time required for the current to decrease to $$1/e of $$its initial value.

Question 3

Which of the following best describes the behavior of the charge $$Q(t) on $$the capacitor in an RC circuit as time increases?

Accepted Answer

$$Q(t)$$ increases and asymptotically approaches $$C \cdot 	ext{emf}.$$

Question 4

A magnet is cut in half. What happens to the magnetic poles?

Accepted Answer

Each piece becomes a new magnet with both a north and a south pole.

Question 5

Which of the following is the correct SI unit for magnetic field strength?

Accepted Answer

Tesla (T)

Question 6

The Earth's magnetic field is primarily generated by:

Accepted Answer

Electric currents in the Earth's liquid iron core.

Question 7

Which equation gives the magnitude of the magnetic field $$B at a $$distance $$r$$ from a long, straight wire carrying current $$I$$?

Accepted Answer

$$B = \frac{\mu_0$}{2\pi} \frac{I}{r}$$

Question 8

A proton moves perpendicular to a uniform magnetic field. What is the direction of the magnetic force acting on it?

Accepted Answer

Perpendicular to both the velocity and the magnetic field, as given by the right-hand rule.

Question 9

Which of the following best describes the path of a charged particle moving perpendicular to a uniform magnetic field?

Accepted Answer

It moves in a circular path.

Question 10

What is the Lorentz force acting on a particle with charge $$q$$ moving with velocity $$\vec{v} in $$both electric field $$\vec{E}$$ and magnetic field $$\vec{B}$$?

Accepted Answer

$$\vec{F} = q\vec{E} + q\vec{v} 	imes \vec{B}$$

Question 11

Which of the following is a real-world application that relies on strong magnetic fields?

Accepted Answer

Magnetic Resonance Imaging (MRI)

Question 12

If the resistance $$R in an RC $$circuit is doubled, what happens to the time constant $$	au$$?

Accepted Answer

It doubles.

Question 13

Which of the following statements about magnetic field lines is correct?

Accepted Answer

They form continuous closed loops.

Question 14

A current-carrying loop of radius $$R$$ produces a magnetic field at its center. What is the expression for the field if the loop has $$N$$ turns?

Accepted Answer

$$B = \frac{\mu_0$ N I}{2R}$$

Question 15

Why is the Earth's magnetic field essential for life?

Accepted Answer

It deflects harmful charged particles from the solar wind.

Question 16

Which of the following best describes the effect of a magnetic field on a stationary charged particle?

Accepted Answer

There is no force exerted on the particle.

Question 17

If the capacitance $$C in an RC $$circuit is increased, what happens to the rate at which the current decreases?

Accepted Answer

The current decreases more slowly.

Question 18

Which historical region gave its name to the phenomenon of magnetism?

Accepted Answer

Magnesia in Greece

Question 19

Which of the following is true about the Earth's magnetic poles?

Accepted Answer

The magnetic south pole is near the geographic north pole.

RC Circuits and Magnetism: Fundamentals and Applications

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