1
AIPMT 2009
MCQ (Single Correct Answer)
+4
-1
Power dissipated in an LCR series circuit connected to an A.C. source of emf $$\varepsilon $$ is
A
$${{{\varepsilon ^2}\sqrt {{R^2} + {{\left( {L\omega - {1 \over {\omega }}} \right)}^2}} } \over R}$$
B
$${{{\varepsilon ^2}\sqrt {{R^2} + {{\left( {L\omega - {1 \over {C\omega }}} \right)}^2}} } \over R}$$
C
$${{{\varepsilon ^2}R} \over {\sqrt {{R^2} + {{\left( {L - {1 \over {C\omega }}} \right)}^2}} }}$$
D
$${{{\varepsilon ^2}R} \over {\left[ {{R^2} + {{\left( {L\omega - {1 \over {C\omega }}} \right)}^2}} \right]}}$$
2
AIPMT 2008
MCQ (Single Correct Answer)
+4
-1
In an a.c. circuit the e.m.f. ($$\varepsilon $$) and the current

(i)  at any instant are given respectively by
$$\varepsilon $$ = E0sin$$\omega $$t,   $$i$$ = $$I$$0sin($$\omega $$t $$-$$ $$\phi $$)

The average power in the circuit over one cycle of a.c. is
A
$${{{E_0}{I_0}} \over 2}\cos \phi $$
B
$${{E_0}{I_0}}$$
C
$${{{E_0}{I_0}} \over 2}$$
D
$${{{E_0}{I_0}} \over 2}\sin \phi $$
3
AIPMT 2007
MCQ (Single Correct Answer)
+4
-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
A
50%
B
90%
C
10%
D
30%
4
AIPMT 2007
MCQ (Single Correct Answer)
+4
-1
The primary and secondary coils of a transformer have 50 and 1500 turns respectively. If the magnetic flux $$\phi $$ linked with the primary coil is given by $$\phi $$ = $$\phi $$0 + 4t, where $$\phi $$ is webers, t is time in seconds and $$\phi $$0 is a constant, the output voltage across the secondary coil is
A
120 volt
B
220 volts
C
30 volts
D
90 volts.
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