Grade 9 Electricity (current)

Question 1

What is Current

Answer 1

The amount of charges (electrons) that flow past a point in a circuit within a specific time

Question 2

How do we measure charge?

Answer 2

A standardised number of electrons are used to represent one charge; a Coulomb (C)

Question 3

1 Coulomb =

Answer 3

6.24 x 10^-18 electrons

Question 4

How do we measure current?

Answer 4

Using an ammeter we can measure how many Coulombs pass through a wire per a second

Question 5

“I” represents…

Answer 5

Current (measured in Amperes [A])

Question 6

“Q” represents…

Answer 6

Charge (measured in Coulombs [C])

Question 7

“t” represents

Answer 7

Time (measured in seconds [s])

Question 8

Formula for Current

Answer 8

Charge/time

Question 9

Formula for Charge

Answer 9

time x current

Question 10

Formula for time

Answer 10

Charge/current

Question 11

2 characteristics of direct current (D.C.)

Answer 11

• charges move in one direction (neg - pos)

- produced by batteries

Question 12

2 characteristics of alternating current (A.C.)

Answer 12

• charges move in both directions (back and forth)

- produced by generators; used in homes

Question 13

What does EPE stand for?

Answer 13

Electrical Potential Energy

Question 14

What is Electrical Potential Energy?

Answer 14

The energy stored in a group of electrons. The more energy the electrons have, the more electrical potential they have

Question 15

Why is it safe to touch both terminals of a AA battery but unsafe to touch both terminals of a wall outlet?

Answer 15

the AA battery has less EPE than the wall outlet

Question 16

How can we measure EPE?

Answer 16

In circuits we don’t measure the total energy. We measure the difference in the energy the electrons have as they travel across a source or a load

Question 17

Define Voltage

Answer 17

Voltage is the difference in EPE between two points in a circuit