A wire of length Lis drawn such that its diameter is reduced to half of its original diameter. If the initial resistance of the wire were 10 Ω, its new resistance would be
40 Ω
80 Ω
120 Ω
160 Ω
An electric dipole placed in a non-uniform electric field experiences
both a torque and a net force
only a force but no torque
only a torque but no net force
no torque and no net force
If an ideal parallel LC circuit, the capacitor is changed by connecting it to a d.c source which is then disconnected. The current in the circuit
becomes zero instantaneously
grows monotonically
decays monotonically
oscillates instantaneously
Three charges are placed at the vertices of an equilateral triangle of side a as shown in the given figure. The force experienced by the charge placed at the vertex A in a direction normal to BC is
Q2 / 4πε0a2
- Q2 (4πε0a2<)
zero
Q2 / 2πε0a2
A capacitor of capacitance 2μF is connected in the tank circuit of an oscillator oscillating with a frequency of 1 kHz. If the current flowing in the circuit is 2 mA, the voltage across the capacitor will be
0.16 V
0.32 V
79.5 V
159 V
The earth's magnetic field at a given point is 0.5 × 10-5 Wb/m2. This field is to be annulled by magnetic induction at the centre of a circular conducting loop of radius 5.0 cm. The current required to be flown in the loop nearly
0.2 A
0.4 A
4 A
40 A
A frog can be levitated in a magnetic field produced by a current in a vertical solenoid placed below the frog. This is possible because the body of the frog behaves as
paramagnetic
diamagnetic
ferromagnetic
antiferromagnetic
A.
paramagnetic
n the presence of an external magnetic field, the atomic dipoles of paramagnetic substances are aligned along the field. The material gets magnetized and it produces an extra magnetic field in the material in the direction of the field. So for paramagnetic materials, the resultant field is greater than the applied field. As the body of a frog behaves like a paramagnetic substance, the smallest magnetic field on the body of the frog will be strong enough to lift it up.
Figure shown is a distribution of charges. The flux of electric field due to these charges through the surface S is
zero
An electron is travelling along the x-direction. It encounters a magnetic field in the y-direction. Its subsequent motion will be
straight line along the x-direction
a circle in the xz plane
a circle in the yz plane
a circle in the xy plane
The difference in lengths of a mean solar day and a sideral day is about
1 min
4 min
15 min
56 min