The diagram shows an electric circuit with two resistors, R and S - Edexcel - GCSE Physics - Question 5 - 2013 - Paper 1
Question 5
The diagram shows an electric circuit with two resistors, R and S.
(i) R has a resistance of 11 ohms.
Calculate the potential difference across R.
(ii) Use informa... show full transcript
Worked Solution & Example Answer:The diagram shows an electric circuit with two resistors, R and S - Edexcel - GCSE Physics - Question 5 - 2013 - Paper 1
Step 1
Calculate the potential difference across R.
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Answer
To calculate the potential difference (V) across resistor R, we use Ohm's Law, which states:
V=IimesR
where:
I=0.40A (current through R)
R=11Ω (resistance of R)
Substituting the values:
V=0.40A×11Ω=4.4V
Thus, the potential difference across R is 4.4 V.
Step 2
Use information from the diagram to calculate the current in S.
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Answer
Using Kirchhoff's current law,
Itotal=IR+IS
where:
Itotal=0.60A (total current entering junction)
IR=0.40A (current through resistor R)
Thus, we can find current in S:
IS=Itotal−IR=0.60A−0.40A=0.20A
Therefore, the current in S is 0.20 A.
Step 3
A student wants to measure the battery voltage with the battery.
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Answer
The voltmeter should be placed:
B in parallel with the battery. This allows the voltmeter to measure the potential difference across the battery.
Step 4
Explain why the temperature of a resistor increases when a current passes through it.
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Answer
When a current passes through a resistor, it encounters resistance. This resistance causes energy to be dissipated in the form of heat due to collisions between charge carriers (like electrons) and the lattice structure of the material. This leads to an increase in the temperature of the resistor.
Step 5
Explain how LDRs and thermistors can be used to control the current in a circuit.
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Answer
LDRs (Light Dependent Resistors) change their resistance based on light intensity. In bright light, the resistance is low, allowing more current to flow, whereas in darkness, the resistance is high, reducing the current. This property can be used in circuits to adjust the current based on surroundings.
Thermistors also change resistance with temperature. An NTC (Negative Temperature Coefficient) thermistor decreases its resistance as temperature increases, allowing more current to flow when it gets hot. Conversely, a PTC (Positive Temperature Coefficient) thermistor increases resistance with temperature, decreasing current flow when heated. Both components are widely used in temperature sensing and automatic control systems.
