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 V1V1 V2V2 V3V3 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