4.3.3 Action and use of circuit components (3)
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1.
A potential divider circuit is designed to provide a voltage of 6V from a 15V power supply. Two resistors are used. One resistor has a value of 3kΩ. Calculate the value of the second resistor required. Show your working.
The potential divider equation is: V1 / V2 = R1 / R2
We are given V1 = 6V, V2 = 15V - 6V = 9V, and R1 = 3kΩ. We need to find R2.
Rearranging the equation to solve for R2: R2 = R1 * (V2 / V1)
Substituting the values:
R2 = 3kΩ * (9V / 6V)
R2 = 3kΩ * (3/2)
R2 = 4.5kΩ
Answer: 4.5kΩ
2.
Question 2
A variable potential divider is used to obtain a specific voltage for a sensitive component in a circuit. Explain why a variable potential divider is preferred over a fixed resistor for this purpose.
A variable potential divider is preferred over a fixed resistor for obtaining a specific voltage for a sensitive component because it offers greater flexibility and control over the output voltage.
Here's a detailed explanation:
- Flexibility: A variable potential divider allows the output voltage to be easily adjusted by changing the resistance of the variable resistor. This is crucial for fine-tuning the voltage to suit the requirements of the sensitive component.
- Control: A fixed resistor provides a single, fixed output voltage. A variable potential divider provides a range of output voltages, allowing for precise control.
- Sensitivity: Using a fixed resistor to obtain a specific voltage might not be practical if the required voltage is not readily available or if the voltage needs to be adjusted dynamically. A variable potential divider can accommodate these scenarios.
- Tolerance: Fixed resistors have a tolerance value, meaning the actual resistance can deviate from the stated value. This can affect the accuracy of the output voltage. A variable potential divider, when properly calibrated, can provide a more precise and consistent output voltage.
3.
A circuit contains a variable resistor, R. A constant current, I, is passed through the circuit. State, in terms of resistance and current, how the potential difference (p.d.) across the resistor changes.
The potential difference (p.d.) across the resistor is directly proportional to the resistance. Therefore, as the resistance increases, the potential difference increases, provided the current remains constant. This relationship is expressed by Ohm's Law: V = IR.