Q: A stationary electron is placed between two parallel plates separated by $$5.0 \times 10$$^{-3}$$\ \mathrm{m}$$ with a $$100\ \mathrm{V}$$ potential difference. What is the magnitude of the electric field between the plates?

$$2.0 \times 10$$^{4}$$\ \mathrm{V\ m$$^{-1}$$}$$

Q: An electron moves with velocity $$8.0 \times 10^6$\ \mathrm{m\ s$$^{-1}$$}$$ into a uniform magnetic field $$B = 2.1 \times 10$$^{-2}$$\ \mathrm{T} at$$ $$40^\circ to $$the field. What is the radius of the electron's path?

$$1.7 \times 10$$^{-3}$$\ \mathrm{m}$$

Q: A beam of electrons travels at $$2 \times 10^6$\ \mathrm{m\ s$$^{-1}$$}$$ between two plates $$1 \times 10$$^{-3}$$\ \mathrm{m}$$ apart with a $$1000\ \mathrm{V}$$ potential difference. What magnetic field is needed to keep the electrons moving straight?

$$1 \times 10$$^{-1}$$\ \mathrm{T}$$\ into the page

Q: A pair of parallel plates are $$5.00 \times 10$$^{-3}$$\ \mathrm{m}$$ apart with a $$1000\ \mathrm{V}$$ potential difference. What is the electric field strength between the plates?

$$2.0 \times 10$$^{5}$$\ \mathrm{V\ m$$^{-1}$$}$$

Question 1

A positively charged ion travels at $$250\ \mathrm{m\ s$$^{-1}$$}$$ between two parallel plates with an electric field of $$200\ \mathrm{V\ m$$^{-1}$$}. A $$magnetic field is applied perpendicular to both the velocity and the electric field so that the ion passes through undeflected. What is the required magnitude of the magnetic field?

Accepted Answer

$$0.8\ \mathrm{T}$$

Question 2

A stationary electron is placed between two parallel plates separated by $$5.0 	imes 10$$^{-3}$$\ \mathrm{m}$$ with a $$100\ \mathrm{V}$$ potential difference. What is the magnitude of the electric field between the plates?

Accepted Answer

$$2.0 	imes 10$$^{4}$$\ \mathrm{V\ m$$^{-1}$$}$$

Question 3

An electron is fired in a vacuum towards a screen. With no electric field, it hits at point $$P. $$With a uniform electric field turned on, it hits at $$Q ($$lower than $$P). If a $$proton is fired under the same conditions, where does it strike?

Accepted Answer

Above $$P$$, at $$A$$

Question 4

A region contains a constant magnetic field and a constant electric field. How will these fields affect a stationary electron?

Accepted Answer

Only the electric field will exert a force.

Question 5

A charged non-magnetic particle is moving in a magnetic field. Which of the following does NOT affect the magnetic force on the particle?

Accepted Answer

The velocity component parallel to the magnetic field direction

Question 6

An electron moves with velocity $$8.0 	imes 10^6$\ \mathrm{m\ s$$^{-1}$$}$$ into a uniform magnetic field $$B = 2.1 	imes 10$$^{-2}$$\ \mathrm{T} at$$ $$40^\circ to $$the field. What is the radius of the electron's path?

Accepted Answer

$$1.7 	imes 10$$^{-3}$$\ \mathrm{m}$$

Question 7

A beam of electrons travels at $$2 	imes 10^6$\ \mathrm{m\ s$$^{-1}$$}$$ between two plates $$1 	imes 10$$^{-3}$$\ \mathrm{m}$$ apart with a $$1000\ \mathrm{V}$$ potential difference. What magnetic field is needed to keep the electrons moving straight?

Accepted Answer

$$1 	imes 10$$^{-1}$$\ \mathrm{T}$$\ into the page

Question 8

Which of the following situations exerts the greatest magnetic force on a proton, given all fields are equal in magnitude?

Accepted Answer

Proton moving perpendicular to the field

Question 9

An alpha particle ($$+2e) $$and a proton are placed at equal distances from two large charged plates. Which best describes their motion?

Accepted Answer

Alpha particle moves with a quarter the acceleration of the proton.

Question 10

A negatively charged particle is accelerated from rest between two parallel plates. The potential difference and final velocity squared are measured. Which equation relates these quantities?

Accepted Answer

$$qV = \frac{1}{2}mv^2$

Question 11

A disc magnet has its poles on opposite flat surfaces. A wire is placed on the disc and moves in the direction of the arrow when a DC battery is connected. What is the direction of the field and current?

Accepted Answer

Field is vertically upward, current from Y to X

Question 12

A proton travels at constant velocity in a vacuum. An electric and a magnetic field are turned on, both perpendicular to the velocity and to each other. What is the resulting path of the proton?

Accepted Answer

A helical path

Question 13

An electron is moving near a long straight wire. When a current is applied, the electron experiences a force in the same direction as the current. What was the electron's initial direction of motion?

Accepted Answer

Opposite to the current direction

Question 14

A pair of parallel plates are $$5.00 	imes 10$$^{-3}$$\ \mathrm{m}$$ apart with a $$1000\ \mathrm{V}$$ potential difference. What is the electric field strength between the plates?

Accepted Answer

$$2.0 	imes 10$$^{5}$$\ \mathrm{V\ m$$^{-1}$$}$$

Question 15

A stationary electron is placed in a region with a uniform magnetic field and a uniform electric field. What is the initial acceleration of the electron?

Accepted Answer

$$a = \frac{eE}{m}$$

Question 16

A proton enters a region with perpendicular electric and magnetic fields such that $$E = vB. $$What is the net force on the proton?

Accepted Answer

Zero

Question 17

A negatively charged cylinder is fixed near a positively charged plate. What is the direction of the electric field lines between them?

Accepted Answer

From the plate to the cylinder

Question 18

An electron enters a region between two parallel plates with a uniform magnetic field perpendicular to its velocity. What is the direction of the force on the electron due to the magnetic field?

Accepted Answer

Downward

Question 19

A proton moves perpendicular to a uniform magnetic field. If the field strength is doubled, what happens to the radius of the proton's path?

Accepted Answer

It halves

Electric and Magnetic Fields: Charged Particle Motion and Calculations

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