Q: A charged particle moves in a region where both electric and magnetic fields are present. Which equation gives the total force on the particle?

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

Q: A hospital uses a defibrillator that stores $$200 J of $$energy in a capacitor at $$4000 V. $$What is the capacitance of the device?

$$C = \frac{2U}{V^2$} = \frac{2 \times 200}{(4000)^2$} = 0.025$$ \mu F

Question 1

Which of the following best describes the physical meaning of electric field lines?

Accepted Answer

They show the direction of the electric force on a positive test charge at each point.

Question 2

A point charge $$q is $$placed at the center of a spherical shell of radius $$R. $$What is the electric field at a distance $$r$$ from the center, where $$r \u003c R$$?

Accepted Answer

$$E = \frac{q}{4\pi\$$epsilon_0$$ r^2$}$$

Question 3

Which equation correctly expresses Gauss's Law in integral form?

Accepted Answer

$$\oint \vec{E} \cdot d\vec{A} = \frac{q_{enc}}{\$$epsilon_0$$}$$

Question 4

A parallel plate capacitor is connected to a battery. If the distance between the plates is doubled while keeping the charge constant, what happens to the electric field between the plates?

Accepted Answer

It remains the same.

Question 5

Which of the following is a correct expression for the potential energy $$U of a $$system of two point charges $$q_1$$ and $$q_2$$ separated by a distance $$r$$?

Accepted Answer

$$U = \frac{q_1$ q_2$}{4\pi\$$epsilon_0$$ r}$$

Question 6

A dipole is placed in a uniform electric field. What is the torque $$	au$$ experienced by the dipole?

Accepted Answer

$$	au = pE \sin	heta$$

Question 7

Which of the following statements about conductors in electrostatic equilibrium is correct?

Accepted Answer

The electric field inside the conductor is zero.

Question 8

A charged particle moves in a region where both electric and magnetic fields are present. Which equation gives the total force on the particle?

Accepted Answer

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

Question 9

Which of the following best describes the concept of electric potential?

Accepted Answer

It is the work done per unit charge to move a charge from infinity to a point in space.

Question 10

A spherical conductor of radius $$R$$ carries a total charge $$Q. $$What is the electric field just outside its surface?

Accepted Answer

$$E = \frac{Q}{4\pi\$$epsilon_0$$ R^2$}$$

Question 11

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

Accepted Answer

$$\vec{E} = -
abla V$$

Question 12

A hospital uses a defibrillator that stores $$200 J of $$energy in a capacitor at $$4000 V. $$What is the capacitance of the device?

Accepted Answer

$$C = \frac{2U}{V^2$} = \frac{2 	imes 200}{(4000)^2$} = 0.025$$ \mu F

Question 13

Which of the following is true about the energy stored in a parallel plate capacitor?

Accepted Answer

$$U = \frac{1}{2}CV^2$

Question 14

A student connects three capacitors in series: $$C_1 = 2$ \mu F, C_2$ = 3$$ \mu F, and $$C_3 = 6$ \mu F. What is the equivalent capacitance?

Accepted Answer

$$C_{eq} = \left(\frac{1}{2} + \frac{1}{3} + \frac{1}{6}\$$right)^{-1}$$ = 1$$ \mu F

Question 15

Which of the following best explains why the electric field inside a hollow conducting shell is zero?

Accepted Answer

The charges on the conductor rearrange themselves to cancel any internal field.

Question 16

A patient receives an electric shock from a faulty medical device. If the device delivers a current of $$0.05 A $$for $$0.2 s$$, how much charge passes through the patient?

Accepted Answer

$$Q = I t = 0.05 	imes 0.2 = 0.01 C$$

Question 17

Which of the following is a correct statement about the superposition principle for electric fields?

Accepted Answer

The net electric field at a point is the vector sum of the fields produced by each charge.

Question 18

A charged ring of radius $$R$$ carries a total charge $$Q. $$What is the electric field at the center of the ring?

Accepted Answer

$$E = 0$$

PHY 131: University Physics II – Electromagnetism (Syllabus & Study Guide)

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