Question
Download Solution PDFThe value of unknown current in CRO is measured by:
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SSC JE Electrical 06 Jun 2024 Shift 2 Official Paper - 1
Answer (Detailed Solution Below)
Option 2 : ratio of voltage measured on CRO to standard resistance
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Detailed Solution
Download Solution PDF- The value of unknown current in CRO is measured by the ratio of voltage measured on CRO to standard resistance.
- CRO is a very versatile instrument in the laboratory for the measurement of voltage, current, frequency, and phase angle of any electrical quantity.
- We cannot directly measure power by using CRO.
- The current is measured indirectly by measuring the voltage drop across an impedance.
- A Lissajous figure is a pattern that is displayed on the screen when sinusoidal signals are applied to both horizontal & vertical deflection plates of CRO.
- These are used to measure the frequency of the given signals and the phase difference between the signals.
- From the shape of the Lissajous pattern displayed on the CRO screen information about relative phases of signals and the frequency ratio of signals can be determined.
- It is not used for precise measurement; it depends on the type of signal.
- If one frequency is an integral multiple (harmonic) of the other, the pattern will be steady. If not, the figure will not be stationary.
Concept:
Voltage measurement using CRO:
Measurement of D.C.Voltage:
- Deflection on a CRO screen is directly proportional to the voltage applied to the deflecting plates.
- Therefore, if the screen is first calibrated in terms of known voltage. i.e. the deflection sensitivity is determined , the direct voltage can be measured by applying it between a pair of deflecting plates.
- The amount of deflection so produced multiplied by the deflection sensitivity, gives the value of direct voltage.
Measurement of A.C voltage:
- To measure the alternating voltage of sinusoidal waveform, The A.C. signal, from the signal generator, is applied across the y – plates.
- The voltage(deflection) sensitivity band switch (Y-plates) and time base band switch (X-plates) are adjusted such that a steady picture of the waveform is obtained on the screen.
- The vertical height i.e. peak-to-peak height is measured.
- When this peak-to-peak height is multiplied by the voltage(deflection) sensitivity (n) i.e. volt/div, we get the peak-to-peak voltage (2Vo). From this we get the peak voltage (Vo).
Last updated on May 29, 2025
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