Board exam

In a region, the electric potential varies as V = 10 – 50x, where V is in volts and x in meters. The electric field in the region is :

1. A10 N/C along +x
2. B10 N/C along –x
3. C50 N/C along +x
4. D50 N/C along –x

A long straight wire of circular cross-section (radius a) carries a steady current I. The current is uniformly distributed across this cross-section. The magnitude of the magnetic field produced at a point at a distance (a/2) from the axis of the wire will be

1. AZero
2. Bμ₀I/(2πa)
3. Cμ₀I/(4πa)
4. Dμ₀I/(6πa)

The shape of the interference fringes in Young’s double-slit experiment, when the distance between the slit and the screen is very large as compared to the slit-separation, is nearly

1. Astraight
2. Bparabolic
3. Ccircular
4. Dhyperbolic

An electromagnetic wave passes from vacuum into a dielectric medium with relative electrical permittivity (3/2) and relative magnetic permeability (8/3). Then, its

1. Awavelength is doubled and frequency remains unchanged.
2. Bwavelength is doubled and frequency is halved.
3. Cwavelength is halved and frequency remains unchanged.
4. Dwavelength and frequency both will remain unchanged.

In a series LCR circuit, the voltage across the resistor, capacitor and inductor is 10 V each. If the capacitor is short circuited, the voltage across the inductor will be

1. A10 V
2. B5√2 V
3. C5/√2 V
4. D10√2 V

Electromagnetic waves used in a diagnostic tool in medicine have a wavelength range

1. A1 nm to 10⁻³ nm
2. B400 nm to 1 nm
3. C1 mm to 700 nm
4. D0.1 m to 1 mm

A concave lens of focal length 10 cm is cut into two identical plano-concave lenses. The focal length of each lens will be

1. A20 cm
2. B30 cm
3. C40 cm
4. D5 cm

Two heaters rated as (P₁, V) and (P₂, V) are connected in series across a dc source of V/2 volt. The power consumed by the combination will be –

1. A(P₁ + P₂)
2. B(P₁ + P₂)/2
3. CP₁P₂/[2(P₁ + P₂)]
4. DP₁P₂/[4(P₁ + P₂)]