Electricity

Question 1

We buy electrical energy in units called

Answer 1

Kilowatt hours (kWh)

Question 2

1kW = ? W

Answer 2

1000

Question 3

1kW charged by Eskom =

Answer 3

R1,70

Question 4

Paying for electricity formula

Answer 4

Cost = power x time x rate

Question 5

Source of the electric current

Answer 5

Electrical cells

Question 6

In a cell -

Answer 6

Chemical energy is converted into electrical energy

Question 7

Series circuit only provides

Answer 7

One pathway for the charge to move

Question 8

Charge:
1. Unit
2. Symbol

Answer 8

1. Coulomb (C)
2. Q

Question 9

Current:
1. Unit
2. Symbol

Answer 9

1. Amperes (A)
2. I

Question 10

Time:
1. Unit
2. Symbol

Answer 10

1. Seconds (s)
2. t

Question 11

Resistance:
1. Unit
2. Symbol

Answer 11

1. Ohms (Ω)
2. R

Question 12

Potential Difference:
1. Unit
2. Symbol

Answer 12

1. Volts (V)
2. Voltage (V)

Question 13

Effects of an electric current

Answer 13

• Heating effect
• Magnetic effect
• Chemical effect

Question 14

Magnetic effect

Answer 14

• When an electric current flows in a conducting wire, a magnetic field develops in the space around the conductor
• Magnetic field is in the form of concentric circles around the conductor

Question 15

Series Circuit current

Answer 15

A1 = A2 = A3

Question 16

Parallel Circuit current

Answer 16

A1 = total current
A1 = A2 + A3

Question 17

Current formula

Answer 17

Current = charge moved ÷ time taken
I = Q ÷ t

Question 18

When a cell is in a complete circuit …

Answer 18

The chemicals (chemical energy) react with each other

Question 19

The charge are given _________ energy they need to ______

Answer 19

Potential
Start moving through the circuit

Question 20

When a charge receives more energy

Answer 20

It releases more energy

Question 21

Why is a voltmeter connected in parallel?

Answer 21

Because it measures potential difference across the ends of a cell/resistor (light bulb)

Question 22

Why is an ammeter connected in series?

Answer 22

So that all the current flows through the ammeter and can be measured

Question 23

Voltmeter connected in ….

Answer 23

Parallel

Question 24

Ammeter connected in ….

Answer 24

Series

Question 25

Voltmeter has ________ resistance because

Answer 25

Very high It forces current to flow through the cell/lightbulb not through the voltmeter

Question 26

Ammeter has _______ resistance because

Answer 26

Low It allows the current to flow through the ammeter so that it can measure it

Question 27

Work done =

Answer 27

Energy transferred

Question 28

1 Volt =

Answer 28

1 J per Coulomb

Question 29

Ohmic Resistor

Answer 29

- The graph for V against I is a straight line that goes through the origin - Relationship between current and potential difference is directly proportional

Question 30

Non-Ohmic resistor

Answer 30

- The graph for V against I is not a straight line

Question 31

Resistance formula

Answer 31

Resistance = potential difference ÷ current R = V ÷ I

Question 32

State Ohm’s Law

Answer 32

Current through a conductor is directly proportional to the potential difference across the conductor at constant temperature

Question 33

Factors that affect resistance

Answer 33

- Type of material - Length of conductor - Thickness of conductor - Temperature of material

Question 34

Type of metal used

Answer 34

Different conducting materials have different resistances

Question 35

Length of conductor

Answer 35

- More length = more resistance - Less length = less resistance - Resistance is directly proportional to the length of metal conductor

Question 36

Thickness of conductor

Answer 36

- Thinner conductor = more resistance - Thicker conductor = less resistance - Resistance is inversely proportional to the thickness of metal conductor - Inversely proportional graph = hyperbola

Question 37

Temperature of conductor

Answer 37

- Hotter conductors = more resistance - Cooler conductors = less resistance

Question 38

Potential Difference in Series

Answer 38

The sum of potential difference across each individual resistor is equal to the potential difference across the battery

Question 39

Potential Difference in Parallel

Answer 39

The potential difference across each resistor in parallel is equal to each other and equal to the potential difference across the battery

Question 40

Resistors in series are called

Answer 40

Potential dividers

Question 41

Resistors in parallel are called

Answer 41

Current dividers

Question 42

Kilowatt hour is another

Answer 42

Unit for energy