288. A 0-300V voltmeter has a guaranteed accuracy of 2 per cent of full-scale reading. If the voltage measured by this instrument is 180 V, then the limiting error will be
A. less than 2%
B. less than 3% but greater than 2%
C. less than 4% but greater than 3%
289. Which one of the following statements regarding Hay bridge and Maxwell bridge is correct?
A. Hay bridge is same as Maxwell bridge having resistor R1 in parallel with C1 in one arm
B. Hay bridge has R1 in series with C1 with Maxwell bridge has R1 in parallel with C1
C. Hay bridge has R1 in parallel with C1 and Maxwell bridge has R1 in series with C1
D. Hay bridge and Maxwell bridge are similar but Hay bridge is used to measure unknown capacitance while Maxwell bridge is used to measure unknown inductance
290. Which one of the following is most suitable for measuring very small capacitances?
A. Transformer ratio-arm bridge
B. Schering bridge Wiens bridge
C.(e) De-Saute bridge
291. Which of the following are the requirements of a CRO (cathode ray oscilloscope) or display of high frequency sinal (magahertz)?I. Input capacitance should be low. 2. Cathode ray tube Shold be provided with post-acceleration.3. Shrot persistance phosphors should be used in the screen. 4. Electromagnetic focussing and deflection system Should be used. Select the correct answer using the codes given below : Codes :
A. 1, 2 and 4
B. 1, 3 and 4
C. 1, 2 and 3
D. 2, 3 and 4
292. A 1000/5 A bar primary current transformer has the ratio and phase error at its rated current with a certain secondary burden of ? 0.4 per cent and +30 minutes respectively. If the number of secondary turns is reduced by unity, the new ratio error and phase error at the rated current and for the same burden will be respectively.
A. ?0.24 per cent and + 30 minutes
B. + 0.26 per cent and + 30 minutes
C. +2.24 per cent and = 30 minutes
D. zero and + 30 minutes
293. The Controlling torque and the electromagnetic damping of the fluxmeter are
A. small and heavy respectively
B. heavy and small respectively
C. both heavy
D. both small
294. If an induction type energy meter runs fast, it can be slowed down by adjusting the
B. light load
C. position of braking magnet and making it move closer to the centre of the disc
D. position of braking magnet and making it move away from the centre of the disc.
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