Resistance on a wire RPA

• At least 15% of the marks in your exam will come from questions relating to required practicals
• Zero error is a reading on a measuring instrument when the value should be zero, which is a systematic error
• By the end of this video, you should be able to describe how to investigate the factors affecting the resistance of electrical circuits
• Increasing the resistance in a circuit by using a longer wire is useful and is found in a variable resistor
• The resistance of the wire is directly proportional to the length
• Investigating factors affecting the resistance of a circuit

  1. Use a battery, an ammeter, a voltmeter, and a length of wire

  2. Measure the current in the circuit with the ammeter and the potential difference across the wire with the voltmeter

  3. Calculate the resistance using the equation: resistance (ohms) = potential difference (volts) / current (amp)
• To reduce heating effects, use a low potential difference to keep the current low and turn off the current between readings
• A variable resistor contains a long piece of wire in a coil, and by changing the length of the wire, the current running through it can be adjusted
• A variable resistor is used to control the potential difference across the lamp in a circuit
• You can find questions on this and all the other required practicals in the revision workbook