An electrical cable of copper has just one wire of radius 9 mm. Its resistance is 5Ω. The single wire of the cable is replaced by 6 different well-insulated copper wires each of radius 3 mm. The total resistance of the cable will now be equal to:
270 Ω
90 Ω
45 Ω
7.5 Ω
A current of 2 amperes flowing through a conductor produces 80 joules of heat in ten seconds. The resistance of the conductor is:
0.5 Ω
2 Ω
4 Ω
20 Ω
A thermoelectric refrigerator works on
Joule effect
Seebeck effect
Peltier's effect
Thermionic effect
A small circular flexible loop of wire of radius 'r' carries a current I. It is placed in a uniform magnetic field B. The tension in the loop will be doubled if :
I is doubled
B is halved
r is doubled
Both B and I are doubled
Two parallel wires carrying current in the same direction attract each other because of :
the potential difference between them
mutual inductance between them
the electric force between them
the magnetic force between them
D.
the magnetic force between them
Two parallel wires carrying currents in the same direction attract each other because magnetic forces on the two wires act towards each other.
A hydrogen atom is paramagnetic. A hydrogen molecule is
diamagnetic
paramagnetic
ferromagnetic
none of these
A galvanometer has a resistance of 400 Ω and deflects full scale for a current of 0.2 mA through it. The shunt resistance required to covert it into 3A ammeter is :
0.027 Ω
0.054 Ω
0.0135 Ω
none of these
The power factor of a series LCR circuit when at resonance is :
zero
0.5
1.0
Depends on values of L, C and R
For high frequency, capacitor offers :
more resistance
less resistance
zero resistance
none of these