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P7: Quiz 9 – Answers

P7: Quiz 9 – Answers

1) total resistance = potential difference ÷ current, or R = V ÷ I

2)

a) Increases

b) Decreases

3)

a)

2)

a) Increases

b) Decreases

3)

a)

*You can use a cell or battery.**Also, you can have a voltmeter around the cell/ battery.*b) Create a circuit with 1 resistor and take a reading for the current from the ammeter; the ammeter can be placed anywhere on the circuit in series with the resistor. We work out the total resistance by dividing the potential difference of the battery (source PD) by the current on the ammeter.

We then add another identical resistor in series and find the total resistance of the circuit by dividing the source PD by the current on the ammeter.

We keep adding more resistors in series and repeat the process of finding total resistance until we have around 6-8 identical resistors in the circuit.

c)

We then add another identical resistor in series and find the total resistance of the circuit by dividing the source PD by the current on the ammeter.

We keep adding more resistors in series and repeat the process of finding total resistance until we have around 6-8 identical resistors in the circuit.

c)

*A straight-line graph like what is shown below.*4)

a)

*You can use a cell or battery.*

*Also, you can have a voltmeter around the cell/ battery.*

b) Create a circuit with 1 resistor and take a reading for the current from the ammeter. We work out the total resistance by dividing the potential difference of the battery (source PD) by the current on the ammeter.

We then add another identical resistor in parallel and find the total resistance of the circuit by dividing the source PD by the current on the ammeter.

We keep adding more identical resistors in parallel and repeat the process until we have around 6-8 identical resistors in the circuit.

c)

We then add another identical resistor in parallel and find the total resistance of the circuit by dividing the source PD by the current on the ammeter.

We keep adding more identical resistors in parallel and repeat the process until we have around 6-8 identical resistors in the circuit.

c)

*A curved graph like what is shown below.*5) We can add a voltmeter in parallel around the cell or battery. The location of the voltmeter is shown on the diagram below.

**Questions**

*Click here for a printable PDF of the graphs in this quiz.*

1) What is the calculation for finding total resistance in a circuit?

2)

a) For series circuits, does adding more identical resistors increase or decrease the total resistance of the circuit?

b) For parallel circuits, does adding more identical resistors increase or decrease the total resistance of the circuit?

3) This question is about investigating how the total resistance of a series circuit changes with the number of identical resistors.

a) Draw a diagram of the circuit that we would use to measure the total resistance in a series circuit for 2 identical resistors. Assume that we know the potential difference of the power source (which can be a cell or battery).

b) Explain how we can investigate how the total resistance of a series circuit is affected by the number of identical resistors.

c) On the graph below, draw how the total resistance of a series circuit changes with the number of identical resistors.

4) This question is about investigating how the total resistance of a parallel circuit changes with the number of identical resistors.

a) Draw a diagram of the circuit that we would use to measure the total resistance in a parallel circuit for 2 identical resistors. Assume that we know the potential difference of the power source (which can be a cell or battery).

b) Explain how we can investigate how the total resistance of a parallel circuit is affected by the number of identical resistors.

c) On the graph below, draw how the total resistance of a parallel circuit changes with the number of identical resistors.

5) Let’s suppose that we did not know the potential difference of our cell or battery. Describe how we could modify our circuits to find the potential difference of the cell or battery. Feel free to draw a diagram.