 # Electric Current and Voltage

In this worksheet, students will learn what electric current and voltage are and how we measure them. Key stage:  KS 3

Curriculum topic:   Physics: Electricity and Electromagnetism

Curriculum subtopic:   Current Electricity

Difficulty level:   ### QUESTION 1 of 10

Current is the amount of electricity flowing around a circuit. Current carries energy to the components of the circuit; that is why light bulbs you use at school light up. Large current makes bulbs bright, whereas a low current would make them dim.

Current is measured using ammeters. Diagram 1 shows an analogue ammeter, whereas diagram 2 shows a digital multimeter, which is used as an ammeter amongst other uses. You are likely to use a digital ammeter at school these days.  Diagram 1 Diagram 2

An ammeter is connected in a circuit in series. This means it is part of the circuit loop (see diagram). The position of the ammeter does not really matter, because the current is the same anywhere in the circuit. Current is not used up as it goes around the circuit. The unit of measuring current is called ampére. We abbreviate this as amps and the symbol is A. Current in a circuit can be changed by changing the circuit components. For example, if a circuit has one bulb and the current is 0.3 A, it will drop if we add another bulb. Light bulbs have very small wires in them called filaments (see the orange wire in bulb picture). Filaments make it very hard for the current to flow, so adding another one makes it even harder. We say that filaments carry resistance, which makes it harder for current to go through them. Resistance is measured in Ohms (Ω). The formula used to calculate resistance is:

resistance = voltage / current

Voltage is the measurement of how much energy is transferred by electricity. It is measured in volts (V) with a device called a voltmeter. A voltmeter looks like an ammeter but it measures voltage. Voltmeters are always connected in a circuit in parallel to a component (see example in diagram: the voltmeter, shown as V, is connected in parallel to the light bulb). Cells have a voltage marked on them. The bigger the voltage, the higher the current. Chemicals inside cells provide the voltage.

What is current?

the amount of electricity flowing around a circuit

the difference in electrical energy

What does current carry?

electricity

energy

voltage

Is this statement true or false?

Large currents make light bulbs bright.

true

false

What device would you use to measure current?

a voltmeter

an ammeter

What is the symbol for the unit we measure current in?

V

C

A

How is a voltmeter always connected to a circuit?

series

parallel

What are the very thin wires in a light bulb called?

Is this statement true or false?

Filaments make it easy for electricity to flow through.

true

false

How can we increase current?

Tick two options.

removing a light bulb from a circuit

adding a light bulb to a circuit

increasing the voltage

decreasing the voltage

How is voltage in a circuit provided?

chemicals in the light bulb

chemicals in the wires

chemicals in the cell

• Question 1

What is current?

the amount of electricity flowing around a circuit
EDDIE SAYS
Current is the amount of electricity flowing around a circuit.
• Question 2

What does current carry?

energy
EDDIE SAYS
Current carries energy.
• Question 3

Is this statement true or false?

Large currents make light bulbs bright.

true
EDDIE SAYS
It is true. Large currents make light bulbs bright.
• Question 4

What device would you use to measure current?

an ammeter
EDDIE SAYS
Current is measured using ammeters.
• Question 5

What is the symbol for the unit we measure current in?

A
EDDIE SAYS
Current is measured in amps (A).
• Question 6

How is a voltmeter always connected to a circuit?

parallel
EDDIE SAYS
A voltmeter is always connected in parallel to a circuit component.
• Question 7

What are the very thin wires in a light bulb called?

filaments
EDDIE SAYS
Filaments are very thin wires in light bulbs.
• Question 8

Is this statement true or false?

Filaments make it easy for electricity to flow through.

false
EDDIE SAYS
The statement is false. Filaments make it very hard for current to flow through.
• Question 9

How can we increase current?

Tick two options.

removing a light bulb from a circuit
increasing the voltage
EDDIE SAYS
We can increase current by removing a circuit component, like a light bulb, and increasing the voltage.
• Question 10

How is voltage in a circuit provided?

chemicals in the cell
EDDIE SAYS
Voltage is provided by chemicals in cells.
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