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Questions and Answers
What is the primary function of a resistance box?
In a rheostat, which terminal is used to achieve variable resistance?
When using a milli-ammeter with different ranges, what does selecting a higher range do to the measured current?
What can be inferred about the milli-ammeter readings provided in the example with a 1.0 mA range and a 3.0 mA range?
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What is the function of the 'wiper' in a rheostat?
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Study Notes
Resistance Box
- Contains multiple resistors that can be activated by inserting keys.
- Resistors are connected between two thick copper conductors for efficient current flow.
- Designed for easy selection of desired resistance values via key operation.
Rheostat
- Functions as a resistance coil to provide variable resistance.
- Features two fixed terminals and one adjustable sliding terminal (wiper).
- Can be utilized solely as a variable resistor using the sliding and one fixed terminal.
- Also serves as a potential divider when fixed terminals are connected to a battery, allowing voltage adjustment through the slider.
Example: Pathfinder Build-28
- A multi-range milli-ammeter constructed with interchangeable shunts and a microampere range galvanometer.
- Measures current in a circuit; for 1.0 mA range selection, it indicates I₁ = 1.0 mA, and for 3.0 mA range, it shows I₂ = 1.5 mA.
- The true current (I₀) in the circuit without the milli-ammeter is calculated by understanding the shunt's impact on current measurement.
- The range increment indicates an increase by a factor of approximately 10³, with the shunt representing the effective resistance seen by the milliammeter.
- Thevenin parameters (In and Rn) across the ammeter are essential for analyzing circuit behavior with different shunt resistances (S₁ for 1 mA and S₂ for 3 mA ranges).
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Description
Explore the concepts of resistance boxes and rheostats in this quiz. Understand their functions, components, and applications in circuit design. Test your knowledge on measuring current and adjusting resistance values effectively.
