P4 Required Practicals

Question 1

Mnemonic: Tigers Sometimes Set Traps, Always Record Their Every Move

Describe the method for investigating the resistance of a wire depending on its length

Answer 1

• Tape the ends of the wire to the mat
• Set the wire length to 20 cm with crocodile clips
• Set the power supply to 1V or 1.5V
• Turn on the switch
• Adjust the variable resistor if the ammeter is above 1A
• Record the meter readings
• Turn off the switch
• Expand the wire length by 10 cm and repeat
• Move the length up to 70 cm

Question 2

Describe the method for investigating the relationship between current and potential difference for a component

Answer 2

1. With the power supply switched off, set up the circuit as shown (draw circuit diagram)
2. Set potential difference at (find out how many volts)
3. Starting with the variable resistor at its lowest resistance (so that the current is at its highest), measure the current and potential difference for the component
4. Switch off power supply
5. Increase the resistance of the variable resistor in about six steps between the minimum and maximum resistances, and each time measure the current and potential difference for the component. Switch off power supply between readings