The temperature of the black body increases from T to 2T. The factor by which the rate of emission will increase, is?
4
2
16
8
Two similar coils are kept mutually perpendicular such that their centres coincide. At the centre, find the ratio of the magnetic field due to one coil and the resultant magnetic field through both coils, if the same current is flown.
1:3
1:2
A conducting sphere of radius R = 20 cm is given by a charge Q = 16μC. What is E at centre?
3.6×106 N/C
1.8×106 N/C
Zero
0.9×106 N/C
C.
Zero
The value of E at the centre of the sphere is zero. Since the centre of the sphere is placed within the Gaussian surface. The use of Gauss law to examine the electric field of a charged sphere shows the electric field enviornment outside the sphere is identical to that of point charge.
Therefore the potential is the same as that of a point charge
hence E=0
A coil having N turns carry a current as shown in the figure. The magnetic field intensity at point P
Zero
An electron moves at right angle to a magnetic field of 1.5×10-2 T with a speed of 6 x 107 m / s. If the specific charge of the electron is 1.7x 1011 C/ kg. The radius of the circular path will be
2.9 cm
3.9 cm
2.35 cm
2 cm
When a certain current is passed in the circuit as shown in figure, 10 kcal of heat is produced in 5 Ω resistance. How much heat is produced in 4 Ω resistance?
4 kcal
2 kcal
5 kcal
3 kcal
If an insulated non-conducting sphere of radius R has charge density ρ. The electric field at a distance r from the centre of sphere (r > R) will be
An L.C. circuit is in the state of resonance. If C = 0.1F and L = 0.25 Henry. Neglecting ohmic resistance of circuit. What is the frequency of oscillations?
1007 Hz
100 Hz
100 Hz
500 Hz