A straight conductor of length l carrying a current I, is bent in the form of a semicircle. The magnetic field (in tesla) at the centre of the semicircle is
A coil having an inductance of 0.5 H carries a current which is uniformly varying from 0 to 10 A in 2 s. The emf (in volts) generated in the coil is
10
5
2.5
1.25
If an alternating voltage is represented as E = 141 sin (628 t), then the rms value of the voltage and the frequency are respectively
141 V, 628 Hz
100 V, 50 Hz
100 V, 100 Hz
141 V, 100 Hz
C.
100 V, 100 Hz
A step-down transformer is used on a 1000 V line to deliver 20 A at 120 V at the secondary coil. If the efficiency of the transformer is 80%, the current drawn from the line is
3 A
30 A
0.3 A
2.4 A
For the series LCR circuit shown in the figure, what is the resonance frequency and the amplitude of the current at the resonating frequency ?
2500 rad s-1 and
2500 rad s-1 and 5 A
2500 rad s-1 and
250 rad s-1 and
A red coloured object illuminated by mercury vapour lamp, when seen through a green filter, will appear
red
blue
black
white
Time taken by sunlight to pass through a window of thickness 4 mm whose refractive index is is
2 × 10-4 s
2 × 104 s
2 × 10-11 s
2 × 1011 s
Two thin lenses of focal length 20 cm and 25 cm are in contact. The effective power of the combination is
4.5 D
18 D
9 D
2.5 D
The magnification of the image when an object is placed at a distance x from the principal focus of a mirror of focal length f
In the Young's double slit experiment, the central maxima is observed t0 be I0. If one of the slits is covered, then the intensity at the central maxima will become
I0