Physics

### AB is a potentiometer wire. If the value of R is increased, in which direction will the balance point J shift?

The potential difference across AB dropped as the value of R grew, and therefore the potential gradient across AB decreased.  E' = kl is the formula for this....

### The volume (V) of a monatomic gas varies with its temperature (T), as shown in the graph. The ratio of work done by the gas, to the heat absorbed by it, when it undergoes a change from state to state , is

(1) $\frac{1}{3}$ (2) $\frac{2}{3}$ (3) $\frac{2}{5}$ (4) $\frac{2}{7}$ Solution: Answer is (3) Given process is isobaric so, $\mathrm{dQ}=\mathrm{n} \mathrm{C}_{\mathrm{p}} \mathrm{d} \mathrm{T}$...

### In the figure, two positive charges q2 and q3 fixed along the y-axis, exert a net electric force in the +x direction on a charge q1 fixed along the x-axis. If a positive charge Q is added at (x,0) the force on q1

The correct option is a) shall increase along the positive x-axis.

### Figure shows a lamina in the x-y plane. Two axes z and z’ pass perpendicular to its plane. A force F acts in the plane of lamina at point P as shown. Which of the following are true?a) torque τ caused by F about z-axis is along b) torque τ’ caused by F about z’ axis is alongc) torque τ caused by F about the z-axis is greater in magnitude than that about the z-axisd) total torque is given be τ = τ + τ’

Correct answers are: b) torque τ’ caused by F about z’ axis is along $-\hat{k}$ c) torque τ caused by F about the z-axis is greater in magnitude than that about the z-axis

### If P, Q, R are physical quantities, having different dimensions, which of the following combinations can never be a meaningful quantity?a) b) c) d) e)

Correct answer is d) $PR-Q^{2}/R$ and e) $(R + Q)/P$

### 7.2. Which of the following points is the likely position of the centre of mass of the system shown in the figure. a) A b) B c) C d) D

Answer: The correct answer is option c) C Explanation: Centre of mass represents the mean position of the matter of a system. In the given figure half of the sphere is hollow whereas the second half...

### Show that for a particle in linear SHM the average kinetic energy over a period of oscillation equals the average potential energy over the same period.

The mass of the particle executing simple harmonic motion is $m$. The particle's displacement at a given time $t$ is given by $x=A \sin \omega t$ Velocity of the particle is given as...

### 7.1. The centre of mass of which of the following is located outside the body? a) a pencil b) a shotput c) a dice d) a bangle

Answer: The correct option is d) a bangle. Explanation: The mass of a bangle is distributed along the circumference of the ring shape of the bangle as it is a hollow shape. The center of mass is...

### A mass, fastened to the end of a steel wire of unstretched length , is whirled in a vertical circle with an angular velocity of at the bottom of the circle. The crosssectional area of the wire is Calculate the elongation of the wire when the mass is at the lowest point of its path.

Mass is given as $m=14.5 \mathrm{~kg}$ Length of the steel wire is given as $\mid=1 \mathrm{~m}$ Angular velocity is given as $v=2$ rev/s Cross-sectional area of the wire is given as \$A=0.065 \times...

### a) Derive the expression for the heat produced due to a current I flowing for a time interval t through a resistor R having a potential difference V across its ends. With which name is this relation known? b) How much heat will an instrument of 12W produce in one minute if it is connected to a battery of 12V? c) The current passing through a room heater has been halved. What will happen to the heat produced by it? d) What is meant by the heating effect of current? Give two applications of the heating effect of current. e) Name the material which is used for making the filaments of an electric bulb.

Answer a) The amount of work done when an electric charge Q moves against a potential difference V is: W = Q V = W = Q V = W = Q V = W = Q V (1) We all know that current I = Q/T. IT = Q (2)...

### Explain why, the current that makes the heater element very hot, only slightly warms the connecting wires leading to the heater.

Answer Because of their low resistance, the connecting wires leading to the heater are somewhat warmer than the wires that heat the heater element. This results in a flow of minimal heat generation...

### Why is an electric bulb not filled with air? Explain why argon or nitrogen is filled in an electric bulb.

Answer Because an electric bulb's filament is comprised of tungsten, which would quickly burn if it came into touch with oxygen in the air, it is not filled with air. Unreactive gases like argon and...

### Q10. a) Write down the formula for the heat produced when a current I is passed through a resistor R for time t. b) An electric iron of resistance 20 ohms draws a current of 5 amperes. Calculate the heat produced in 30 seconds.

Answer a) The following is the formula for calculating the amount of heat produced: I2Rt = H b) Assumed R equals 20 5 amps = I t = 30 seconds We are aware of this. I2Rt = H We know H = 15000J by...