The rms value of AC which when passed through a resistor produces heat, which is twice that produced by a steady current of 1.414 A in the same resistor is
2 A
3.46 A
2.818 A
1.732 A
In a series LCR AC circuit, the current is maximum when the impedance is equal to
the reactance
the resistance
zero
twice the reactance
A transformer connected to 220 V mains is used to light a lamp of rating 100 W and 110 V. If the primary current is 0.5 A, the efficiency of the transformer is ( approximately)
60 %
35 %
50 %
90 %
A lamp consumes only 25 % of the peak power in an AC circuit. The phase difference between the applied voltage and the current is
In an L-C-R series circuit, at resonance
the current and voltage are in phase
the impedance is maximum
the current is minimum
the quality factor is independent of R
A step-down transformer increases the input current 4 A to 24 A at the secondary. If the number of turns in the primary coil is 330, the number of turns in the secondary coil is
60
50
55
45
An AC source of voltage E = 20 sin 100 t is connected across a resistance 20 Ω. The rms value of current in the circuit is
1 A
In an L-C-R circuit
the impedance is equal to reactance
the ratio between effective voltage to effective current is called reactance
at resonance the net reactance is zero
at resonance the resistance is equal to the reactance
A step-down transformer with an efficiency of 80% is used on a 1000 V line to deliver 10 A at 100 V at the secondary coil. The current drawn from the line is
1.5 A
2 A
3 A
1.25 A
Identify the wrong statement
Eddy currents are produced in a steady magnetic field
Eddy currents can be minimized by using laminated core
Induction furnace uses eddy current to produce heat
Eddy current can be used to produce breaking force in moving vehicles