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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.
Answer
To find the potential difference across R, we can use Ohm's Law, which is given by: Where:
- V is the potential difference,
- I is the current, and
- R is the resistance.
Given that R has a resistance of 11 ohms and the current through R is 0.4 A, we can substitute these values into the formula: Therefore, the potential difference across R is 4.4 V.
Step 2
Use information from the diagram to calculate the current in S.
Answer
According to Kirchhoff's Current Law, the total current entering a junction must equal the total current leaving the junction. In this circuit, the current entering the junction is 0.6 A (total current) and the current leaving through the resistor R is 0.4 A. Thus, the current in S can be calculated as: So, the current in S is 0.2 A.
Step 3
Step 4
Explain why the temperature of a resistor increases when a current passes through it.
Answer
When a current passes through a resistor, electrical energy is converted into heat due to the resistance against the flow of electrons. This effect is known as Joule heating or resistive heating.
The increase in temperature occurs because the movement of charge carriers (usually electrons) within the resistor generates heat as they collide with the atoms in the resistor material. As the current increases, the resistance converts more electrical energy into thermal energy, causing the temperature of the resistor to rise.
Step 5
Explain how LDRs and thermistors can be used to control the current in a circuit.
Answer
LDRs (Light Dependent Resistors) and thermistors are two types of resistors that change their resistance in response to external conditions, allowing them to control current in a circuit.
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LDR: The resistance of an LDR decreases when light intensity increases, allowing more current to flow through. In a circuit, this can be used in applications such as automatic lighting systems where the LDR detects ambient light levels and adjusts the current to turn lights on or off based on the light availability.
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Thermistor: A thermistor changes its resistance based on temperature. A Negative Temperature Coefficient (NTC) thermistor decreases its resistance as temperature rises, allowing greater current to flow. This feature can be utilized in temperature-sensitive applications like temperature sensing circuits and in circuit protection, where excessive heat generates an increase in current, triggering protective measures.
Both components provide a way to create circuits that react dynamically to changes in environmental conditions.