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
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
A.
0.027 Ω
Required resistance,
= 0.027 Ω
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