Question 1

Which of the following is the correct SI unit for the magnetic field $$\vec{B}$$?

Accepted Answer

$$\mathrm{T} ($$Tesla)

Question 2

The unit of magnetic dipole moment $$\vec{m} in SI $$units is:

Accepted Answer

$$\mathrm{A} \cdot \mathrm{m}^2$$

Question 3

Which statement best describes the behavior of metals and certain other materials when they undergo a phase transition to a superconducting state?

Accepted Answer

They lose all electrical resistance and expel magnetic fields from their interior.

Question 4

According to Kirchhoff's loop rule, the sum of all potential differences $$\sum \Delta V$$ around a closed loop is:

Accepted Answer

$$\sum \Delta V = 0$$

Question 5

Copper ($$\mathrm{Cu}) is $$diamagnetic and aluminum ($$\mathrm{Al}) is $$paramagnetic. Which statement is correct about their magnetic properties?

Accepted Answer

Copper is repelled by magnetic fields, while aluminum is weakly attracted.

Question 6

According to Gauss's law for magnetism, which of the following is always true for the net magnetic flux $$\Phi_B$$ through any closed surface?

Accepted Answer

$$\Phi_B = 0$$

Question 7

The current $$I$$ through a closed loop is related to the circulation of which quantity around the loop?

Accepted Answer

Magnetic field $$\vec{B}$$

Question 8

Which of the following statements about the electric field $$\vec{E} is $$correct?

Accepted Answer

The electric field is conservative, so $$\oint \vec{E} \cdot d\vec{l} = 0$$ for electrostatic fields.

Question 9

According to Faraday's law, the induced emf $$\mathcal{E} in a $$closed loop is given by:

Accepted Answer

$$\mathcal{E} = - \dfrac{d\Phi_B}{dt}$$

Question 10

A capacitor in a circuit is initially uncharged. The switch is closed at $$t=0. $$What is the charge $$Q on $$the capacitor as a function of time $$t$$?

Accepted Answer

$$Q(t) = Q_0$ (1 - e$$^{-t/RC}$$)$$

Question 11

For the circuit shown, what is the time constant $$	au$$?

Accepted Answer

$$	au = RC$$

Question 12

The equation for the loop in an $$RC$$ circuit is:

Accepted Answer

$$\mathcal{E} = IR + \dfrac{Q}{C}$$

Question 13

The current density $$\vec{J}$$ inside a wire carrying current out of the page is given by:

Accepted Answer

$$\vec{J} = \dfrac{I}{\pi a^2$} \hat{z}$$

Question 14

The magnetic field $$\vec{B}$$ inside a long straight wire of radius $$a$$ carrying current $$I at a $$distance $$r \u003c a$$ from the center is:

Accepted Answer

$$\vec{B} = \dfrac{\mu_0$ I r}{2\pi a^2$} \hat{\phi}$$

Question 15

The magnetic field $$\vec{B} at a $$point on the $$y-$$axis at $$y = b \u003e a$$ outside a long straight wire of radius $$a$$ carrying current $$I is$$:

Accepted Answer

$$\vec{B} = \dfrac{\mu_0$ I}{2\pi b} \hat{x}$$

Question 16

The force per unit length between two parallel wires carrying currents $$I_1$$ and $$I_2$$ separated by distance $$b is$$:

Accepted Answer

$$F/L = \dfrac{\mu_0$ I_1$ I_2$}{2\pi b}$$

Question 17

Which of the following is true about the direction of the force between two parallel wires carrying currents in the same direction?

Accepted Answer

The wires attract each other.

Question 18

A long solenoid with $$n$$ turns per unit length carries current $$I. $$What is the magnetic field $$B$$ inside the solenoid?

Accepted Answer

$$B = \mu_0$ n I$$

Question 19

Which of the following best describes the difference between paramagnetic and diamagnetic materials?

Accepted Answer

Paramagnetic materials are weakly attracted to magnetic fields, while diamagnetic materials are weakly repelled.

Electromagnetism: Magnetic Fields, Circuits, and Current

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