Electrical and ...

Resistance is determined by the voltmeter ammeter method. The voltmeter reads 100 V with a probable error of ±12 V and ammeter reads 10 A with a probable error of ±2 A. The probable error in the computed value of resistance will be nearly

When voltage of E = 20 sin ωt + 40 sin (3ωt + 30°) + 50 sin (ωt + 60°) is applied to an electrodynamometer voltmeter. The reading of the instrument is – (in V)

Two wattmeters are connected to measure the power consumed by a 3-ϕ load with a power factor of 0.4. The total power consumed by the load as indicated by the two wattmeters is 30 kW. The difference between the two wattmeter readings is _____ kW

A 50 A, 230 V meter on full load test makes 61 revolutions in 37 seconds. If the normal disc speed is 520 revolutions per kWh, the percentage error is_

A thermocouple ammeter gives full scale deflection for a current of 10 amp. When it reads one fourth of the scale, then what is the current through the meter.

The coil of a moving iron voltmeter has a resistance of 5,000 Ω at 15° C at which temperature it reads correctly when connected to a supply of 200 V. If the coil is wound with wire whose temperature coefficient at 15° C is 0.004. The percentage error in the reading when the temperature is 50° C is ________

An ammeter has a PMMC instrument with a coil resistance of R_m = 99 Ω and an FSD current of 0.1 mA. Shunt resistance R_s = 1 Ω. Determine the total current passing through the ammeter at full-scale deflection and half full-scale deflection.

An electrostatic voltmeter consists of two attracted plates, one movable, and the other fixed. It is observed that the application of 10 kV between the plates results in a pull of 5 × 10^-3 N on the movable plate. The diameter of the movable plate is 100 mm. Find the change in capacitance resulting from the change in position of the movable plate by 1 mm ______ (up to 2 decimal)

The law of deflection of a moving iron ammeter is given by I = 4θⁿ ampere, where θ is the deflection in radian and n is a constant. The self-inductance when the meter current is zero is 10 mH. The expression for self-inductance as a function of θ and n is ________ (here K_C is spring constant)

The power flowing in a 3-phase 3 wire balanced load system is measured by two wattmeter method. The reading of wattmeter A is 7500 W and of wattmeter B is -1500 W. The voltage of the circuit is 200 V at 50 Hz. What is the power factor of the system; and the value of capacitance which must be introduced in each phase to cause the whole of the power measure to appear on wattmeter A.

A 230 V single phase watt hour meter has a constant load of 4 A passing through it for 6 hours at unity power factor. The meter disc makes 2208 revolutions during this period. Calculate the power factor of the load if the number of revolutions made by meter are 1472 when operating at 230 V, and 5 A for 4 hours.

The constant for 3 phase 3 element integrating wattmeter is 0.25 revolution of disc per kWh. If the meter is normally used with a potential transformer of ratio 44000/220 V and the current transformer of ratio 2000/20 A, find the error expressed as a percentage of the correct reading from the following test figures for the instrument only:

Line voltage = 200 V; current 12.50 A; power factor = 0.91

A 20 V dc voltage is measured by analog and digital millimetres. The analog instrument is on its 25 V range, and its specified accuracy is ± 2%. The digital meter has \(3\frac{1}{2}\) digit display with a full-scale range of 200 V and an accuracy of ± (0.6% reading + 1 digit). The accuracy of measurement in analog and digital respectively are

A CRO has an anode voltage 3000 V and parallel deflection plate 3 cm long and 7 mm apart. The screen is 35 cm from the centre of the plates. Find the input voltage required to deflect the beam through 4 cm. The input voltage is applied to the deflecting plates through amplifiers having an overall gain of 100.