Physics

### What is the advantage of using thick metallic strips to join wires in a potentiometer?strips to join wires in a potentiometer?

The advantage of using thick metallic strips is that the resistance of these strips is negligible.

### A long straight cable of length is placed symmetrically along the z-axis and has radius . The cable consists of a thin wire and a co-axial conducting tube. An alternating current sin flows down the central thin wire and returns along the co-axial conducting tube. The induced electric field at a distance from the wire inside the cable is . In , compare the conduction current 10 with the displacement current

The displacement will be, $I_{0}^{\mathrm{d}} / \mathrm{I}_{0}=(\mathrm{am} / \lambda)^{2}$

### Show that the magnetic field at a point in between the plates of a parallel plate capacitor during charging is

Let $I_{d}$ be the displacement current in the magnetic field region between two parallel plate capacitor plates. The magnetic field induction at a point between two capacitor plates at a...

### A variable frequency a.c source is connected to a capacitor. How will the displacement current change with a decrease in frequency?

Capacitive reaction is given as, $\mathrm{Xc}=1 / 2 \mathrm{mf} \mathrm{C}$ As the frequency decreases, $X_ c$ rises, and the conduction current becomes inversely proportional to $X_ c$.

### Why does a microwave oven heats up a food item containing water molecules most efficiently?

Because the microwave's frequency and the resonant frequency of the water molecules are the same, the microwave oven cooks a food item containing water molecules most efficiently.

### An EM wave of intensity I falls on a surface kept in vacuum and exerts radiation pressure on it. Which of the following are true?a) radiation pressure is if the wave is totally absorbedb) radiation pressure is if the wave is totally reflectedc) radiation pressure is if the wave is totally reflectedd) radiation pressure is in the range for real surface

The correct options are: a) radiation pressure is $\mathrm{l} / \mathrm{c}$ if the wave is totally absorbed c) radiation pressure is $2 \mathrm{l} / \mathrm{c}$ if the wave is totally reflected d)...

### A charged particle oscillates about its mean equilibrium position with a frequency of . The electromagnetic waves produced:a) will have a frequency of b) will have a frequency of c) will have a wavelength of d) fall in the region of radiowaves

The correct options are: a) will have a frequency of $10^{9} \mathrm{~Hz}$ c) will have a wavelength of $0.3 \mathrm{~m}$ d) fall in the region of radiowaves

### An alternating current generator has an internal resistance and an internal reactance . It is used to supply power to a passive load consisting of a resistance and a reactance . For maximum power to be delivered from the generator to the load, the value of is equal to(a) zero.(b) .(c) .(d) .

(c) $-X_{g}$.

### Is the momentum conserved when charge crosses a junction in an electric circuit? Why or why not?

Answer: When a charge traverses a junction in an electric circuit, the momentum of the charge does not conserve. This is due to the fact that the drift velocity is directly proportional to the...

### A uniform square plate S and a uniform rectangular plate R have identical areas and masses. Show that

Area of square $=$ area of rectangle $I_{z R}-I_{z S}=m\left(d_{R} / 2\right)^{2}-m\left(d_{S} / 2\right)^{2}$ On solving the above equation, we can get $I_{zR}/I_{zS}>1$

### Two cylindrical hollow drums of radii R and 2R and of a common height h, are rotating with angular velocities ω (anti-clockwise) and ω (clockwise) respectively. Their axes, fixed are parallel and in a horizontal plane separated by (3R + δ). They are now brought in contact What would be the ratio of final angular velocities when friction ceases?

The anticlockwise and clockwise angular velocities of the drum are $\omega_{1}$ and $\omega_{2}$ respectively. When the velocities are equal, there is no force of friction and it is given as...

### A disc of radius R is rotating with an angular speed about a horizontal axis. It is placed on a horizontal table. The coefficient of kinetic friction is .a) what condition should be satisfied for rolling to being?b) calculate the time taken for the rolling to being

a) The condition that needs to be satisfied is $v_{cm}=\omega_{o}R$ b) Frictional force is responsible for allowing rolling motion to occur without the disc slipping.

### A disc of radius R is rotating with an angular speed about a horizontal axis. It is placed on a horizontal table. The coefficient of kinetic friction is .a) what was the velocity of its centre of mass before being brought in contact with the table?b) what happens to the linear velocity of a point on its rim when placed in contact with the table?

a) Before coming into contact with the table, the disc was rotating, and $v_{cm}=0$ was the rest. b) When the revolving disc comes into contact with the table, the linear velocity of the disc...

### Two discs of moments of inertia and about their respective axes and rotating with angular speed and are brought into contact face to face with their axes of rotation coincident.a) does the law of conservation of angular momentum apply to the situation? why?b) find the angular speed of the two-disc system

a) Because there is no external torque on the system and the gravitational and normal reactions to external forces have net torque zero, the equation of conservation of angular momentum can be...

### Why does a solid sphere have a smaller moment of inertia than a hollow cylinder of same mass and radius, about an axis passing through their axes of symmetry?

The moment of inertia is related to the square of the distance between the mass and the rotational axis. The distribution of mass in a solid sphere occurs from the sphere's centre to its radius. In...

### Regarding figure, of a cube of edge a and mass n, state whether the following are true or false.a) the moment of inertia of cube about the z-axis is b) the moment of inertia of cube about z’ is c) the moment of inertia of cube about z’’ is d)

Correct answers are: b) the moment of inertia of cube about z’ is $I_{z}^{\prime}=I_{z}+\frac{m a^{2}}{2}$ d) $I_{x}=I_{y}$

### Choose the correct alternatives:a) for a general rotational motion, angular momentum L and angular velocity ω need not be parallelb) for a rotational motion about a fixed axis, angular momentum L and angular velocity ω are always parallelc) for a general translational motion, momentum p and velocity v is always paralleld) for a general translational motion, acceleration a and velocity v are always parallel

a) Angular momentum L and angular velocity ω do not have to be parallel for a general rotating motion. c) Momentum p and velocity v are always parallel in a typical translational motion.

### For which of the following does the centre of mass lie outside the body?a) a pencilb) a shotputc) a diced) a bangle

Correct answer is d) a bangle

### Einstein’s mass-energy relation emerging out of his famous theory of relativity relates mass (m) to energy (E) as , where c is the speed of light in vacuum. At the nuclear level, the magnitudes of energy are very small. The energy at nuclear level is usually measured in MeV where , the masses are measured in unified equivalent of 1u is 931.5 MeV.a) Show that the energy equivalent of 1 u is 931.5 MeV.b) A student writes the relation as 1 u = 931.5 MeV. The teacher points out that the relation is dimensionally incorrect. Write the correct relation.

a) The energy that is comparable to a given mass can be computed using Einstein's mass-energy relation. $1amu=1u=1.67\times 10^{-27}kg$ On Applying $E=mc^{2}$ we get, E = 931.5 MeV b) As $E=mc^{2}$...

### In an experiment to estimate the size of a molecule of oleic acid, 1mL of oleic acid is dissolved in 19mL of alcohol. Then 1mL of this solution is diluted to 20mL by adding alcohol. Now, 1 drop of this diluted solution is placed on water in a shallow trough. The solution spreads over the surface of water forming one molecule thick layer. Now, lycopodium powder is sprinkled evenly over the film we can calculate the thickness of the film which will give us the size of oleic acid molecule.Read the passage carefully and answer the following questions:a) What would be the volume of oleic acid in each mL of solution prepared?b) How will you calculate the volume of n drops of this solution of oleic.

a) 1 mL of oleic acid is found in every 20 mL of oleic acid. This signifies that 1/20 mL of oleic acid is present in each mL of solution. Adding alcohol dilutes 1 mL of this solution to 20 mL. As a...

### Photon is quantum of radiation with energy E = hv where v is frequency and h is Planck’s constant. The dimensions of h are the same as that of:a) linear impulseb) angular impulsec) linear momentumd) angular momentum

Correct options are b) angular impulse and d) angular momentum

### On the basis of dimensions, decide which of the following relations for the displacement of a particle undergoing simple harmonic motion is not correct:a) y = a sin 2πt/Tb) y = a sin vtc) y = a/T sin (t/a)d) y = a√2 [sin (2 πt/T) – cos (2πt/T)]

Correct answers are b) y = a sin vt and c) y = a/T sin (t/a)

### Which of the following measurements is most precise?a) 5.00 mmb) 5.00 cmc) 5.00 md) 5.00 km

Correct answer is a) 5.00 mm

### The number of significant figures in 0.06900 is:a) 5b) 4c) 2d) 3

The correct answer is b) 4 The number of zeroes to the left of a non-zero integer is not considered relevant, whereas the number of zeroes to the right of a non-zero number is.

### 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...