Electromagnetic Induction — Physics STD 12 Science — Question

A double charged lithium atom is equivalent to hydrogen whose atomic number is 3. The wavelength of required radiation for emitting electron from first to third Bohr orbit in   will be (Ionisation energy of hydrogen atom is 13.6eV)

(a) 182.51 Å

(b) 177.17 Å

(c) 142.25 Å

(d) 113.74 Å

A conducting rod PQ of length L = 1.0 m is moving with a uniform speed v = 2 m/s in a uniform magnetic field B = 4.0T  directed into the paper. A capacitor of capacity C = 10 mF is connected as shown in figure. Then

(a) qA = + 80 mC and qB = – 80 mC

(b) qA = – 80 mC and qB = + 80 mC

(c) qA = 0 = qB

(d) Charge stored in the capacitor increases exponentially with time

The strength of the magnetic field at a point r near a long straight current carrying wire is B. The field at a distance   will be

(a)

(b)

(c) 2B

(d) 4B

In a P-type semiconductor

(a) Current is mainly carried by holes

(b) Current is mainly carried by electrons

(c) The material is always positively charged

(d) Doping is done by pentavalent material

The equation E = pc is valid:

A copper ring is kept horizontal and a bar of magnet is dropped in the direction of the axis of the ring. The acceleration of the falling magnet will be:

The relation between I_p and V_p for a triode is   , Keeping the grid potential constant at 1V, the value of r_p will be

(a) 8 kW

(b) 4 kW

(c) 2 kW

(d) 8 kW

An  object of length 6 cm is placed on the principle axis of a concave mirror of focal length f at a distance of 4f. The length of the image will be

(a) 2 cm

(b) 12 cm

(c) 4 cm

(d) 1.2 cm

Which of the following statement is not true regarding Einsteins mass energy relation?

An average emf of 32V is induced in a coil in which the current drops from 10A to 2A in 0.1s. The inductance of the coil is: