Electrical Measuring Instruments
Physics ⇒ Electricity and Magnetism
Electrical Measuring Instruments starts at 9 and continues till grade 12.
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See sample questions for grade 12
A student uses a voltmeter with a resistance of 10 kΩ to measure the voltage across a 1 kΩ resistor. Will the reading be accurate? Explain.
Calculate the current measured by an ammeter if a shunt of 0.02 Ω is connected in parallel with a galvanometer of resistance 20 Ω, and the galvanometer shows a full-scale deflection at 1 mA.
Calculate the resistance to be connected in series with a galvanometer of resistance 50 Ω to convert it into a voltmeter of range 10 V, if the galvanometer gives full-scale deflection at 2 mA.
Describe how you would use a multimeter to check if a wire is broken inside its insulation.
Describe the difference between analog and digital measuring instruments.
Explain the purpose of calibration in electrical measuring instruments.
Explain the working principle of a moving coil galvanometer.
Explain why a voltmeter is connected in parallel and not in series with a circuit element.
State the function of a shunt in an ammeter.
State the main difference between a moving coil and a moving iron instrument.
A digital multimeter is set to measure resistance, but the probes are not connected to any component. The display shows 'OL' or a very high value. What does this indicate?
A laboratory technician needs to calibrate a voltmeter. Briefly describe the steps and precautions that should be taken during the calibration process.
A moving coil galvanometer has a coil of resistance 100 Ω and gives a full-scale deflection for a current of 5 mA. Calculate the value of the shunt resistance required to convert it into an ammeter of range 2 A.
A moving coil galvanometer is not suitable for measuring alternating current. Explain why.
A voltmeter of resistance 20 kΩ is used to measure the potential difference across a resistor in a circuit. If the internal resistance of the source is not negligible, explain how the voltmeter reading will be affected and why.
Explain why the scale of a moving iron instrument is non-uniform, whereas the scale of a moving coil galvanometer is uniform.
State the reason why an ammeter should have as low a resistance as possible.
