Comprehension Check

1. If you have a charge of 1.0C, how many electrons have been removed from the object?

2. What voltage is created if a charged particle is placed 2.5cm from a -1.0mC charge?

3. What electric field is created between two plates, separated by 5.0cm with a voltage of 250V?

Comprehension Check

1. 6.25x1018

2. -360 000 000V

3. 5 000N/C

Motion of a Charged Particle in an Electric Field

Physics 12Adv

Forces

Draw a free body diagram for an electron placed in a uniform electric field where the field is directed into the ground

Fe

Fg

Consider

What happens when a charged particle is placed (with zero initial velocity) inside a uniform electric field?

Draw a picture to show an electron placed at the negative plate that is creating a uniform field

If the field is created using 250V with plates separated by 1.0cm, determine how fast the electron is moving when it gets to the positive plate (ignore gravity)

Cathode Ray Tube

Electrons are emitted (boiled off) from the cathode and then accelerated to the anode

It is also possible to deflect the beam using an electric field

Moving Charged Particle

If a moving charged particle enters an electric field, it will also experience forces due to the field

However, we must now include both the motion prior to entering the field as well as the forces it experiences in the field to predict its path

Moving Charged Particle

Equations of Motion

Recall: However, in 2D, we need four EOM’s:

0

00

2

2vtatv

dtvta

td

yyy

yyy

y

xxx

xxx

x

vtatv

dtvta

td

vtatv

dtvta

td

0

00

2

0

00

2

2

2

Example

An electron enters a uniform electric field of -350N/C while travelling horizontally to the field at 450m/s. If the field is 5.0cm wide, determine:How long it takes the electron to transit the

fieldHow far it “falls” while travelling through the

fieldHow fast it is going when it exits the field