Energy & Electricity

Investigating voltage and current

Lesson objectives

To be able to clearly define the meaning of the terms “current”, and “voltage / potential difference”

To be able to correctly use a voltmeter in a variety of circuits

To understand the relationship between potential difference and current.

Electrical current

Current is a measure of…….

Current is measured using …

An ammeter is always placed in series in a circuit

Voltage / potential difference(p.d.)

Voltage is a measure of the energy carried by the current.

(Technically it is a measure of the difference in energy between two points – hence the name potential difference).

Voltage / potential difference(p.d.)

Voltage is measured with a voltmeter.

Voltmeters are always placed in parallel in a circuit.

Measuring voltage

V1

V2 V3

V1 =

V2 =

V3 =

Measuring voltage

V1 = V2 + V3

The total voltage across the battery is equal to the sum of the voltage across the constituent parts.

Relationship between current and voltage – across a filament lamp

Set up this circuit and measure the current and voltage across the lamp at different values – measure at least 5 values

A

V

Voltage (V) Current (A)

Relationship between current and voltage – across a filament lamp

Now plot a graph of voltage against current for the filament lamp circuit.

Current, A

Voltage, V

Relationship between current and voltage – across a fixed resistor

Set up this circuit and measure the current and voltage across the lamp at different values – measure at least 5 values

A

V

Voltage (V) Current (A)

Relationship between current and voltage – across a fixed resistor

Now plot a graph of voltage against current for the fixed resistor circuit.

Current, A

Voltage, V