AIPMT 2007 | Alternating Current Question 53 | Physics

AIPMT 2007

MCQ (Single Correct Answer)

-1

A transformer is used to light a 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 amp, the efficiency of the transformer is approximately

50%

90%

10%

30%

AIPMT 2006

MCQ (Single Correct Answer)

-1

A coil of inductive reactance 31 $$\Omega $$ has a resistance of 8 $$\Omega $$. It is placed in series with a condenser of capacitative reactance 25 $$\Omega $$. The combination is connected to an a.c. source of 110 V. The power factor of the circuit is

0.33

0.56

0.64

0.80

AIPMT 2006

MCQ (Single Correct Answer)

-1

The core of a transformer is laminated because

ratio of voltage in primary and secondary may be increased

energy losses due to eddy currents may be minimised

the weight of the transformer may be reduced

rusting of the core may be prevented.

AIPMT 2006

MCQ (Single Correct Answer)

-1

A transistor-oscillator using a resonant circuit with an inductor L (of negligible resistance) and a capacitor C in series produce oscillations of frequency $$f$$. If L is doubled and C is changed to 4C, the frequency will be

$$f/2$$

$$f/4$$

$$8f$$

$$f/2$$$$\sqrt 2 $$

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