# Tag: physics

### Questions Related to physics

While making a battery ___________  of a cell is connected to ________ of other cell.

1. negative terminal , negative terminal

2. positive terminal , negative terminal

3. positive terminal , positive terminal

4. neutral terminal ,negative terminal

Correct Option: B
Explanation:

While making a battery, negative end of battery is connected to positive terminal of other cell and so on.

When the two terminals of a battery are connected directly with a wire then:

1. More electrical energy is stored in the cell

2. The chemicals get used up very fast

3. No current flows in the wire

4. None of these

Correct Option: B
Explanation:
When the two terminals of a battery are connected directly with a wire there will be a low resistance path for the current to flow. The wire will get heated a little bit (depends on the diameter of the wire less the diameter more heat) and the battery will be quickly discharged. During depletion, it may become very hot, emit gasses, and possibly explode. The shorting wires will draw heavy current that may melt the wire or even cause them to soften and break.

Many devices such as.............. use batteries-

1. Torches

2. Transistors, toys

3. T.V. remote controls

4. All of these

Correct Option: D
Explanation:

Many devices such as----------------use battery

Torches
Transistors, toys
T.V remote controls
All of these use batteries.

A charge is kept at the centre of a shell. Shell has charge Q uniformally distibuted over its surface and radius R. The force on the central charge due to the shell is :

1. towards left

2. towards right

3. upward

4. zero

Correct Option: D
Explanation:

Electric field at the centre of shell is zero when charge is uniformally distributed over surface of shell .

Hence the force on the charge at the centre is zero.

A hollow conducting sphere of charge does not have electric field at

1. outer point

2. interior point

3. beyond $2m$

4. beyond $100m$

Correct Option: B
Explanation:

$E=0$, at any point inside the sphere

Assertion: Electric field inside a current carrying wire is zero.
Reason: Net charge in a current carrying wire is non zero.

1. A

2. B

3. C

4. D

Correct Option: C

The rupture of air medium occurs at $E=3\times 10^6 \ V/m$. The maximum charge that can be given to a sphere of diameter $5 \ m$ will be (in coulomb):

1. $2\times 10^{-2}$

2. $2\times 10^{-3}$

3. $2\times 10^{-4}$

4. $2\times 10^{-5}$

Correct Option: B
Explanation:

Given, $E _o= 3 \times 10^6 \ V/m;$  Diameter of sphere $= 5 \ m$

Electric field on the surface of the sphere $= \cfrac {KQ}{R^2}$

$E _o= \cfrac {KQ}{R^2}$

$Q= \cfrac {R^2E^o}{K}= \cfrac {6.25 \times 3 \times 10^6}{9 \times 10^9}$

$= 2 \times 10^{-3}\ C$

A spherical shell of mass $m$ and radius $R$ filled completely with a liquid of same mass and set to rotate about a vertical axis through its centre has a moment of inertia ${I _1}$ about the axis$.$ The liquid starts leaking out of the hole at the buttom$.$ If moment of inertia of the system is ${I _2}$ when the shell is half filled and ${I _3}$ is the moment of inertia when entire water drained off$.$ then $:$

1. $\dfrac{{{I _1}}}{{{I _2}}} \approx 1.5$

2. $\dfrac{{{I _{ _1}}}}{{{I _2}}} \approx 0.67$

3. $\dfrac{{{I _1}}}{{{I _3}}} \approx 1.6$

4. $\dfrac{{{I _2}}}{{{I _3}}} \approx 1.4$

Correct Option: C
Explanation:

Moment of inertia of a shell$,$ ${I _3} = \frac{2}{3}M{R^2}$

Moment of inertia of a completely filled sphere$,$ ${I _1} = \frac{2}{3}M{R^2} + \frac{2}{5}M{R^2} = \frac{{16}}{{15}}M{R^2}$
Moment of inertia of a half sphere$,$ ${I _2} = \frac{2}{3}M{R^2} + \frac{2}{5}\frac{M}{2}{R^2} = \frac{{26}}{{30}}M{R^2}$
Hence,
option $(C)$is correct answer.

A positive charge q is placed in a spherical cavity made in a positively charged sphere. The centres of sphere cavity are displaced by a small distance $\overrightarrow l$. Force on charge q is:

1. in the direction parallel to vector $\overrightarrow l$

3. in a direction which depends on the magnitude of charge density in sphere

4. direction can not be determined.

Correct Option: D

At all points inside a uniform spherical shell -

1. gravitational intensity and gravitational potential both are zero

2. gravitational intensity and gravitational potential both are non- zero

3. gravitational intensity is non- zero and gravitational potential both are zero

4. gravitational intensity is zero and gravitational potential both are non-zero

Correct Option: A
Explanation:

Gravity Force Inside a Spherical Shell. The net gravitational force on a point mass inside a spherical shell of mass is identically zero! Physically, this is a very important result because any spherically symmetric mass distribution outside the position of the test mass m can be build up as a series of such shells