Question 1

A positive test charge $$q_0 is $$placed at point $$P$$ near a charged body $$A. If $$the force on $$q_0 is$$ $$\vec{F}_0$$, what is the electric field $$\vec{E} at $$point $$P$$ due to body $$A$$?

Accepted Answer

$$\vec{E} = \frac{\vec{F}_0}{q_0$}$$

Question 2

Which statement best describes the direction of the electric field created by a positive point charge?

Accepted Answer

The electric field vectors point radially outward from the charge.

Question 3

A negative test charge is placed in an electric field created by a positive source charge $$Q. $$What is the direction of the force on the test charge?

Accepted Answer

Opposite to the direction of the electric field.

Question 4

Which of the following best describes the electric field lines between two parallel plates with opposite charges?

Accepted Answer

The field lines are parallel and evenly spaced, indicating a uniform electric field.

Question 5

Given two point charges, $$q_1 = +3$$\ \mu	ext{C}$$ and q_2$ = -3\ \mu	ext{C}$$, separated by a distance $$d$$, what is the direction of the electric field at the midpoint between them?

Accepted Answer

From $$q_1 to$$ $$q_2$$

Question 6

The magnitude of the electric field at a distance $$r$$ from a point charge $$q is $$given by which equation?

Accepted Answer

$$E = \frac{1}{4\pi\$$varepsilon_0$$} \frac{|q|}{r^2$}$$

Question 7

A rod of length $$l$$ has a uniform charge per unit length $$\lambda$$ and total charge $$Q. $$What is the expression for the electric field at a point $$P$$ along the axis of the rod at a distance $$d$$ from one end?

Accepted Answer

$$E = \frac{k_e Q}{d(d+l)}$$

Question 8

A ring of radius $$a$$ carries a total charge $$Q. $$What is the electric field at a point $$P on $$the axis of the ring, a distance $$x$$ from its center?

Accepted Answer

$$E = \frac{1}{4\pi\$$varepsilon_0$$} \frac{Qx}{(x^2$ + a^2$)^{3/2}$$}$

Question 9

Which of the following statements about electric dipoles in a uniform electric field is correct?

Accepted Answer

A dipole experiences a torque that aligns it with the electric field.

Question 10

If the electric field at a point due to multiple charges is to be found, which principle must be used?

Accepted Answer

The superposition principle: add the electric fields from each charge as vectors.

Question 11

A disk of radius $$R$$ has a uniform surface charge density $$\sigma. $$What is the electric field at a point $$x on $$the axis of the disk?

Accepted Answer

$$E = \frac{\sigma}{2\$$varepsilon_0$$} \left(1 - \frac{x}{\sqrt{x^2$ + R^2$}}\right)$$

Question 12

Which of the following is the correct unit for electric field strength?

Accepted Answer

$$	ext{N/C}$$

Question 13

A parallel-plate capacitor produces a uniform electric field. Which of the following is true about the field between the plates?

Accepted Answer

The electric field is the same in magnitude and direction at every point between the plates.

Question 14

A point charge $$Q is $$placed at the origin. What is the direction of the electric field at the point $$(1, -1)$$ meters?

Accepted Answer

Along the vector from the origin to $$(1, -1)$$

Question 15

Which of the following best describes the electric field lines for two equal positive charges placed near each other?

Accepted Answer

Field lines originate from both charges and repel each other, never crossing between the charges.

Question 16

A dipole is placed in a uniform electric field and released from rest. What is its subsequent motion?

Accepted Answer

It rotates to align with the electric field.

Question 17

Which of the following is the correct expression for the torque $$	au on an $$electric dipole $$\vec{p} in a $$uniform electric field $$\vec{E}$$?

Accepted Answer

$$\vec{	au} = \vec{p} 	imes \vec{E}$$

Week 1 Lec. 3

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