A wave travelling along positive x-axis is given by y=A sin (ωt -kx). If it is reflected from rigid boundary such that 80% amplitude is reflected then equation of reflected wave is
y = A sin(ωt - kx)
y = - 0.8 A sin(ωt + kx)
y = 0.8 A sin(ωt + kx)
y=A sin(ωt + 0.8 kx)
Standing waves are formed on a string when interference occurs between two waves having
the same amplitude travelling in the same direction with no phase difference between them
the same amplitude, travelling in the opposite direction with no phase difference between them
different amplitudes travelling in the same direction
different amplitudes travelling in the opposite direction
Two capacitors, one 4 pF and the other 6 pF, connected in parallel, are charged by a 100 V battery. The energy stored in the capacitors is
1.2 × 10−8 J
2.4 × 10−8 J
5.0 × 10−8 J
1.2 × 10−6 J
The electrical resistivity of a sample
is proportional to its length
is proportional to the area of cross-section
is inversely proportional to the length
neither depends on the length nor on the area of cross-section
A voltmeter of resistance 998 is connected across a cell of emf 2V and internal resistance 2. The potential difference across the voltmeter is
1.99 V
3.5 V
5 V
6 V
A solenoid of length 5O cm and a radius of cross-section 1 cm has 1000 turns of wire wound over it. If the current carried is 5 A, the magnetic field on its axis, near the centre of the solenoid is approximately (permeability of free space = T-m/A)
0.63 × 10−2 T
1.26 × 10−2 T
2.51 × 10−2 T
6.3 T
A conducting square loop of side L and resistance R moves in its plane with a uniform velocity v, perpendicular to one of its sides. A magnetic field of induction B, constant in space and time and pointing perpendicularly into the plane of the square, exists everywhere in space. The current induced in the loop is
BLv/R in the clockwise direction
BLv/R in the anticlockwise direction
2 BLv/R in the clockwise direction
zero
A sinusoidal voltage of peak value 300 V and an angular frequency = 400 rad/s is applied to series L-C-R circuit, in which R = 3 , L = 20 mH and C = 625 µF. The peak current in the circuit is
30 A
60 A
100 A
60 A
B.
60 A
The impedance of the circuit is
Z =
XL = L = 400 × 20 × 10−3 = 8 H
XC =
Z = = 5
i =
A circuit contains a capacitor and inductance each with negligible resistance. The capacitor is initially charged and the charging battery is disconnected. At subsequent time, the charge on the capacitor will
increase exponentially
decrease exponentially
decrease linearly
remain constant
A transformer of 100% efficiency has 200 turns in the primary and 40000 turns in secondary. It is connected to a 220 V main supply and secondary feeds to a 100 kresistance. The potential difference per turn is
1.1 V
25 V
18 V
11 V