C3 - Current, Charge, and Time

Question 1

What determines electrical properties of a metal?

Answer 1

The movement of electrons around positive ion cores.

Question 2

What is a current?

Answer 2

A flow of charged particles each with the same charge in coulombs.

Question 3

What’s the formula for charge? (total)

Answer 3

Q =nq where Q=total charge, n=number of atoms, and q=charge of each.

Question 4

Why is current constant in series?

Answer 4

The charges all have the same speed and travel in the same direction.

Question 5

What’s Kirchhoff’s first law?

Answer 5

At junctions, the current is split. It tends to take the past of least resistance. It = I1 + I2.
This is due to the conservation of charge.

Question 6

In a cell, how is electrical potential energy produced?

Answer 6

Chemical reactions create a difference in potential energy. This leads to a positive terminal and a negative terminal. Positive ions are repelled by the positive terminal and lose energy travelling ‘downhill,’ while electrons are repelled by the negative terminal and lose energy.

Question 7

When charges move, their …… …… energy changes, so w….k is done. W =

Answer 7

electrical potential, work, W= change in energy (E)

Question 8

What is voltage ?

Answer 8

The potential energy difference per unit charge between two points.

Question 9

What is voltage’s formula?

Answer 9

V = E/Q = W/Q so W=VQ.

Question 10

What is joule heating?

Answer 10

Electrons often collide with positive ion cores. They lose electrical potential energy which dissipates through joule heating. This can happen in the cell due to internal resistance.

Question 11

What is power? Give a few relevant formulae..

Answer 11

Power is the rate at which energy is transferred.

P=IV =W/t =VQ/t = VIt/t = IV P=1^2R