2. Electricity (required practical 4 - current/pd characteristics)

Question 1

What is the practical?

Answer 1

investigating the current/voltage characteristics of circuit components

Question 2

What are the steps for the practical using a resistor?

Answer 2

1. Use the voltmeter to read the potential difference across the resistor
2. Use the ammeter to read the current through the resistor and record these values in a table
3. Adjust the variable resistor and record the new readings on the voltmeter and the ammeter
4. Switch the direction of the battery
5. Take several readings of the potential difference and the current
6. Plot a graph of current against the potential difference for a resistor

Question 3

What does switching the direction of the battery do for the resistor experiment?

Answer 3

• it means that the direction of the potential difference has now reversed
• the voltmeter and ammeter should have negative values

Question 4

What are the steps for the practical using a filament lamp?

Answer 4

1. Use the voltmeter to read the potential difference across the filament lamp
2. Use the ammeter to read the current through the filament lamp and record these values in a table
3. Adjust the variable resistor and record the new readings on the voltmeter and the ammeter
4. Switch the direction of the battery
5. Take several readings of the potential difference and the current
6. Plot a graph of current against the potential difference for a filament lamp

Question 5

What are the steps for the practical using a diode?

Answer 5

1. Set up a series circuit including an extra resistor and milliammeter
2. Adjust the variable resistor a number of times and record the potential difference and the current
3. Do this with the battery in the forward and backwards direction
4. Plot a graph of current against the potential difference for a diode

Question 6

Why is there an extra resistor in the circuit for the diode?

Answer 6

Because diodes are very easily damaged by a high current, so the extra resistor will keep the current relatively low, protecting the diode

Question 7

Why is a milliammeter needed in the circuit for a diode?

Answer 7

because the current will be very low, a very sensitive ammeter, milliammeter is needed