Electric fields

Question 1

Value of e (electric charge on a proton)

Answer 1

1.6 * 10^-19 C

Charge on electron is -e

Question 2

Law of conservation of charge

Answer 2

Charge cannot be created or destroyed. Total charge does not change

Question 3

What did the Tolman-Stewart experiment prove?

Answer 3

Electrons are the charge carriers in metals

Question 4

Describe Tolman-Stewart experiment

Answer 4

• If negative electrons are charge carriers, they should be free to move while positive charges stay fixed
• If metal is suddenly accelerated with a very large a, electrons would be thrown back
• Creates excess negative charge at back and excess positive charge at front
• Excess charge was measured-found to be consistent with negative charge carriers in metals

Question 5

Coulomb’s law in words

Answer 5

Electric force between two charges q₁ and q₂ is:
1. Propotional to product of two charges
2. Inversely proportional to square of seperation of charges

Question 6

Coulomb’s law (formula)

Answer 6

F= k (q₁ q₂ /r²)

k = 8.99 * 10⁹ Nm² C^-2 in vaccum/ air

Question 7

Constant k also written as?

Answer 7

1/4πε_o

Question 8

How to test a space for an electric field

Answer 8

If test charge q(positve) experiences an electric force, there is a field. q must be small so it doesn’t disturb the electric field it is trying to detect.

Question 9

Electric field strength formula

Answer 9

E=F/q
electric force per unit charge
∴ E=k(Q/r²

Also applies outside a conducting sphere with charge q on surface