4.2 Electrical quantities

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Question 17

A student investigates a resistor and a filament lamp connected in series.

The student adjusts the position of a crocodile clip on a resistance wire until the potential difference $VLV_{\text{L}}$ . across the lamp is $V3.0\text{ V}$ .

The ammeter used to measure the current $I$ in the circuit has major scale markings at $0.50\text{ A}$ , with $10$ small divisions between each major marking. The pointer is at the $6th6\text{th}$ small division after $A0.20\text{ A}$ .
The voltmeter used to measure the potential difference $VRV_{\text{R}}$ _ across the resistor has major scale markings at $6.0\text{ V}$ , with $10$ small divisions between each major marking. The pointer is at the $4th4\text{th}$ small division after $V4.0\text{ V}$ .

Record the values of $I$ and $VRV_{\text{R}}$ _ for $VV_{\text{L}} = 3.0\text{ V}$ .

[2]

The table below shows the results of this experiment.

$VV_{\text{L}}\text{ / V}$	$AI\text{ / A}$	$VV_{\text{R}}\text{ / V}$
$3.0$
$2.0$	$0.20$	$3.5$
$1.0$	$0.12$	$2.1$

Calculate, and record in the table, the resistance of the lamp $RLR_{\text{L}}$ . and the resistor $RRR_{\text{R}}$ . for each value of $VLV_{\text{L}}$ . Use the equations:

R_{\text{L}} = \frac{V_{\text{L}}}{I} \quad \text{and} \quad R_{\text{R}} = \frac{V_{\text{R}}}{I}

Give all your values of $RLR_{\text{L}}$ . and $RRR_{\text{R}}$ . to a consistent number of significant figures (2 or 3 significant figures).

[3]

Describe the pattern of any change in the value of $RLR_{\text{L}}$ . as $VLV_{\text{L}}$ . decreases.

[1]

State whether your results support the suggestion that the resistance $RRR_{\text{R}}$ . of the resistor is constant. Justify your statement by reference to the calculated values.

[2]

The student wishes to determine the resistance of the lamp $RLR_{\text{L}}$ . when the potential difference across the lamp $VV_{\text{L}} = 0.0\text{ V}$ . Describe how the experiment can be extended to do this with the help of a suitable graph.

[3]

Describe how a variable resistor can be connected into the circuit instead of a resistance wire to change the potential difference across the lamp, and state where a voltmeter must be connected to measure the potential difference across the resistor.

[2]

The student adjusts the position of a crocodile clip on a resistance wire until the potential difference $VLV_{\text{L}}$ . across the lamp is $V3.0\text{ V}$ .

The ammeter used to measure the current $I$ in the circuit has major scale markings at $0.50\text{ A}$ , with $10$ small divisions between each major marking. The pointer is at the $6th6\text{th}$ small division after $A0.20\text{ A}$ .
The voltmeter used to measure the potential difference $VRV_{\text{R}}$ _ across the resistor has major scale markings at $6.0\text{ V}$ , with $10$ small divisions between each major marking. The pointer is at the $4th4\text{th}$ small division after $V4.0\text{ V}$ .

Record the values of $I$ and $VRV_{\text{R}}$ _ for $VV_{\text{L}} = 3.0\text{ V}$ .

VV_{\text{L}}\text{ / V}

AI\text{ / A}

VV_{\text{R}}\text{ / V}

ΩR_{\text{L}}\text{ / }\Omega

ΩR_{\text{R}}\text{ / }\Omega

3.0

2.0

0.20

3.5

1.0

0.12

2.1

4.2 Electrical quantities

Question 17

Markscheme

4.2 Electrical quantities

Question 17

Markscheme

4.2 Electrical quantities

Question 17

4.2 Electrical quantities Questions

4.2 Electrical quantities

Question 17

4.2 Electrical quantities Questions