A candidate connects a moving coil ammeter A and a moving coil voltmeter V and a resistance R as shown. If the voltmeter reads 20 V and the ammeter reads 4 A, then R is
equal to 5Ω
greater than 5Ω
less than 5Ω
none of these
A wire of length L has resistance R. It is bent at mid-point such that the two halves make an angle 90° with each other. The new resistance would be.
R
R
The ratio of magnetic potentials due to a magnetic dipole in the 'end on position' to that in the 'broad side on position' for the same distance from it is
zero
infinite
1
2
B.
infinite
As magnetic potential in the broad side on position is zero, therefore the required ratio must be infinite.
In the unmagnetized state magnetic domains of a magnetic substance are oriented at
60°
90°
randomly
150°
When a ferromagnetic material is heated above its Curie temperature it
gets demagnetised
becomes diamagnetic
behaves like a paramagnetic substance
remains unaffected
A DC circuit contains 10Ω of resistance in series with 10 H coil. The impedance of the circuit is
10 Ω
20 Ω
1 Ω
zero
Two coils of self-inductance L1 and L2 are placed so close together that effective flux in one coil is completely linked with the other. If M is the mutual inductance between them, then
M = L1L2
M = L1/L2
M = L
In an L-R circuit, the current increases to three fourth of its maximum value in 4 s, then the time constant of the circuit is
2loge 2
Two identical galvanometers are taken, one is to be converted into an ammeter and other into a milliammeter. The shunt of milliammeter compared to ammeter is
less
more
zero
none of these
If the vibrations of a string are to be increased by a factor of two, the tension in the string should be made
twice
four times
eight times
half