In electric arc furnace Cu or Iron is melted due to variation of
(a) current
(b) magnetic field
(c) voltage
(d) electric field
(a) current
(b) magnetic field
(c) voltage
(d) electric field
(b) magnetic field
In series R-L-C circuit, quality factor can be improved by
(a) decreasing L
(b) increasing C
(c) decreasing R
(d) decreasing R & L
Obtain the expression for the energy density of magnitude field B produced in the inductor.
In an A.C. circuit, Irms and I₀ are related as
(a) Irms = p I₀
(b) Irms = 2 I₀
(c) Irms = I₀/p
(d) Irms =I₀ / 2
Show that the current leads the voltage in phase by in an ac circuit containing an ideal capacitor.
Length of a hollow tube is 5 m, its outer diameter is 10 cm and thickness of its wall is 5 mm. If resistivity of the material of the tube is 1.7 x 10⁻⁸ Ωm, then the resistance of the tube will be
(a) 5.6 × 10⁻⁵ Ω
(b) 2 × 10⁻⁵ Ω
(c) 4 × 10⁻⁵ Ω
(d) None of these
The force between two charges, when placed in free space, is 5N. if they are in a medium of relative permittivity 5, the force between them will be
A. 1N
B. 25N
C. 2.5N
D. 1/5N
Two capacitors of capacitance 6 µF and 4 µF are put in series across a 120 V battery. What is the potential difference across the 4 µF capacitor?
(a) 72 V
(b) 60 V
(c) 48 V
(d) zero
A Galvanometer of resistance 10 Ω gives full-scale deflection when 1 mA current passes through it. The resistance required to convert it into a voltmeter reading upto 2.5 Volt is;
a) 9800 Ω
b) 2490 Ω
c) 4980 Ω
d) 9880 Ω.
In electric arc furnace Cu or Iron is melted due to variation of
(a) current
(b) magnetic field
(c) voltage
(d) electric field
Two coherent monochromatic light beams of intensities I and 41 superimpose. The maximum and minimum possible intensities in the resulting beam are:
(a) 5I and I
(b) 5I and 3I
(c) 3I and I
(d) 9I and I
Two capacitors of 3 μF and 6 μF are connected in series with a battery of P.d. 12 V. The P.d. across 3μF and 6μF capacitors respectively will be :
(a) 8 V, 4 V
(b) 6 V, 6 V
(c) 4 V, 8 V
(d) 9 V, 3 V