Physics NCERT Exemplar Solutions Class 12th Chapter Six

A small bar magnet is moved through a coil at constant speed from one end to the other. Which of the following series of observations will be seen on the galvanometer G attached across the coil?

Three positions shown describe:

(a) The magnet's entry

(b) Magnet is completely inside and

(c) Magnet's exit

A transformer operating at primary voltage 8 kV and secondary voltage 160V serves a load of 80 k.W. Assuming the transformer to be ideal with purly resistive load and working on unity power factor, the loads in the primary and secondary circuit would be

A air bubble of radius 1 cm in water has an upward acceleration 9.8 cm^-2 . The density of water is 1 gmcm^-3 and water offers negligible drag force on the bubble. The mass of the bubble is: (g=980 cm/s²)

Particle $A$ of mass $m_A=\frac{m}{2}$ moving along the $x$ -axis with velocity $v_0$ collides elastically with another particle $B$ at rest having mass $m_B=\frac{m}{3}$ . If both particles move along the $x$ axis after the collision, the change $\mathrm{\Delta }\lambda$ in de-Broglie wavelength of particle $A$ , in terms of its de-Broglie wavelength $\left({\lambda }_0\right)$ before collision is:

A wire $A$ , bent in the shape of an arc of a circle, carrying a current of $2\mathrm{A}$ and having radius $2\mathrm{c}\mathrm{m}$ and another wire $B$ , also bent in the shape of arc of a circle, carrying a current of $3\mathrm{A}$ and having radius of $4\mathrm{c}\mathrm{m}$ , are placed as shown in the figure. The ratio of the magnetic fields due to the wires $A$ and $B$ at the common centre $O$ is:

A man of 60kg is running on the road and suddenly jumps into stationary trolly car of mass 120kg. Then, the trolly car starts moving with velocity 2ms^-1. The velocity of the running man was _________ ms^-1, when he jumps into the car

A pendulum is suspended by a string of length 250 cm. The mass of the bob of the pendulum is 200g. The bob is pulled aside until the string is at 60° with vertical as shown in the figure. After releasing the bob, the maximum velocity attained by the bob will be_________ ms^-1. (if g = 10m/s²)

A coil of inductance 1H and resistance 100 $\Omega$ is connected to a battery of 6.V. Determine approximately:

(A)The time elapsed before the current acquires half of its steady – state value.

(B)The energy stored in the magnetic field associated with the coil at instant 15ms after the circuit is switched on. (Given In 2 = 0.693, e3/2 = 0.25)

The change in the magnitude of the volume of an ideal gas when a small additional pressure $\mathrm{\Delta }\mathrm{P}$ is applied at a constant temperature, is the same as the change when the temperature is reduced by a small quantity $\mathrm{\Delta }T$ at constant pressure. The initial temperature and pressure of the gas were $300\mathrm{K}$ and 2 atm. respectively. If $\left|\mathrm{\Delta }T\right|=C\left|\mathrm{\Delta }P\right|$ then value of $C$  in (K/atm) is .

Match the thermodynamics processes taking place in a system with the correct conditions. In the table: $\mathrm{\Delta }\mathrm{Q}$ is the heat supplied, $\mathrm{\Delta }\mathrm{W}$ is the work done and $\mathrm{\Delta }\mathrm{U}$  is change in internal energy of the system. Match the following: