M.C.Q (1 Marks)

MCQ 11 Mark

A resistor of resistance $R$ is connected to an ideal battery. If the value of $R$ is decreased, the power dissipated in the resistor will:

✓
Increase.
B
Decrease.
C
Remain unchanged.
D
none

Answer

Correct option: A.

Increase.

Power $=\frac{\text{V}^2}{\text{R}},\text{R}\downarrow\text{thanpower}\uparrow$
Because Power $\propto\frac{1}{\text{R}}.$

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MCQ 21 Mark

Two non$-$ideal batteries are connected in parallel. Consider the following statements:

The equivalent emf is smaller than either of the two emfs.
The equivalent internal resistance is smaller than either of the two internal resistances.

A
Both $A$ and $B$ are correct.
B
$A$ is correct but $B$ is wrong.
✓
$B$ is correct but $A$ is wrong.
D
Both $A$ and $B$ are wrong.

Answer

Correct option: C.

$B$ is correct but $A$ is wrong.

Equivalent emf $\in_0=\frac{\in_1\text{r}_1+\in_2\text{r}_2}{\text{r}_1+\text{r}_2}$

Equivalent resistance $=\text{r}_0=\frac{\text{r}_1\text{r}_2}{\text{r}_1+\text{r}_2}$
$\phi$ The equivalent emf is smaller than either of the two emfs.
$\phi$ The equivalent internal resistance is smaller than either of the two internal resistances.

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MCQ 31 Mark

Two resistors $A$ and $B$ have resistances $R_A$ and $R_B$, respectively, and $R_A$

A
$\rho _\text{A}>\rho _\text{B}$
B
$\rho _\text{A}=\rho _\text{B}$
C
$\rho _\text{A}<\rho _\text{B}$
✓
The information is not sufficient to find the relation between $\rho _\text{A}$ and $\rho _\text{B}.$

Answer

Correct option: D.

The information is not sufficient to find the relation between $\rho _\text{A}$ and $\rho _\text{B}.$

$\text{R}=\frac{\rho \ell}{\text{A}}$
Resistance is depend on Material, length Area.
So $RA < RB$ is information is not sufficient to ding.
The relation between $\rho_\text{A}$ and $\rho_\text{B}.$

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MCQ 41 Mark

Two non$-$ideal batteries are connected in series. Consider the following statements:

The equivalent emf is larger than either of the two emfs.
The equivalent internal resistance is smaller than either of the two internal resistances.

A
Each of $A$ and $B$ are correct.
✓
$A$ is correct but $B$ is wrong.
C
$B$ is correct but $A$ is wrong.
D
Each $A$ and $B$ are wrong.

Answer

Correct option: B.

$A$ is correct but $B$ is wrong.

Equivalent emf $=\hat{\text{I}}_1+\hat{\text{I}}_2$
$\text{R}_\text{eq}=\text{r}_1+\text{r}_2$
Equivalent emf $=\hat{\text{I}}_1+\hat{\text{I}}_2\Big\{\hat{\text{I}}_1>\hat{\text{I}}_2\Big\}$
$\text{R}_\text{eq}=\text{r}_1+\text{r}_2$

$\phi$ The equivalent emf is larger than either of the two emfs.
$\phi$ The equivalent internal resistance is smaller than either of the two internal resistances.

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MCQ 51 Mark

As the temperature of a metallic resistor is increased, the product of its resistivity and conductivity:

A
Increases.
B
Decreases.
C
Remains constant.
✓
May increase or decrease.

Answer

Correct option: D.

May increase or decrease.

Explanation:
The product of resistivity and conductivity is independent of temperature. As the temperature of a metallic resistor is increased, the resistivity increases and conductivity decreases. Hence, both the conductivity and resistivity of the metallic resistor nullify the effect of the change in temperature.

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MCQ 61 Mark

Two resistors $R$ and $2R$ are connected in series in an electric circuit. The thermal energy developed in $R$ and $2R$ are in the ratio :

✓
$1 : 2.$
B
$2 : 1.$
C
$1 : 4.$
D
$4 : 1.$

Answer

Correct option: A.

$1 : 2.$

Thermal Energy developed $= I^2Rt \ ($Because in series, current is same$)$

$\frac{\text{Thermal Energy developedin "R"}}{\text{Thermal Energy developedin "2R"}}=\frac{\text{I}^2\text{Rt}}{\text{I}^2(2\text{R})\text{t}}=\frac{1}{2}$

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MCQ 71 Mark

The product of resistivity and conductivity of a cylindrical conductor depends on:

A
Temperature.
B
Material.
C
Area of cross section.
✓
None of these.

Answer

Correct option: D.

None of these.

Explanation:
Conductivity $\sigma=\frac{1}{\rho }$ Where r is resistivily.
Product of conductity and resistivity = 1.

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MCQ 81 Mark

In an electric circuit containing a battery, the charge (assumed positive) inside the battery:

A
Always goes from the positive terminal to the negative terminal.
✓
May go from the positive terminal to the negative terminal.
C
Always goes from the negative terminal to the positive terminal
D
Does not move.

Answer

Correct option: B.

May go from the positive terminal to the negative terminal.

Explanation:
The charge (Positive) inside the bottery my go from the positive terminal to the negative terminal.

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MCQ 91 Mark

A metallic resistor is connected across a battery. If the number of collisions of the free electrons with the lattice is somehow decreased in the resistor $($for example, by cooling it$),$ the current will:

✓
Increase.
B
Decrease.
C
Remain constant.
D
Become zero.

Answer

Correct option: A.

Increase.

If the number of collisions of the free electrons with the lattice is decreased, then the drift velocity of the electrons increases.
Current i is directly proportional to the drift velocity $'V_d'$ and is given by the following relation:
$\text{i}=\text{neAV}_\text{d}.$

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MCQ 101 Mark

Consider the following two statements:

Kirchhoff's junction law follows from conservation of charge.
Kirchhoff's loop law follows from conservative nature of electric field.

✓
Both $A$ and $B$ are correct.
B
$A$ is correct but $B$ is wrong.
C
$B$ is correct but $A$ is wrong.
D
Both $A$ and $B$ are wrong.

Answer

Correct option: A.

Both $A$ and $B$ are correct.

$\phi$ Kirchhoff's Junction Law follows from conservation of charge.
$\phi$ Kirchhoff's loop law fallows from conservation nature of electric field.

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MCQ 111 Mark

The net resistance of a voltmeter should be large to ensure that:

A
It does not get overheated.
B
It does not draw excessive current.
C
It can measure large potential differences.
✓
It does not appreciably change the potential difference to be measured.

Answer

Correct option: D.

It does not appreciably change the potential difference to be measured.

The net resistance of a voltmeter should be large to ensure that it does not appreciably change the potential difference to be measured.

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MCQ 121 Mark

Which of the following quantities do not change when a resistor connected to a battery is heated due to the current?

A
Drift speed.
B
Resistivity.
C
Resistance.
✓
Number of free electrons.

Answer

Correct option: D.

Number of free electrons.

When a resistor connected to a battery is heated due to the current that causes drift speed, resistivity & resistance may e change But number of free electrons remains same.

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MCQ 131 Mark

As the temperature of a conductor increases, its resistivity and conductivity change. The ratio of resistivity to conductivity:

✓
Increases.
B
Decreases.
C
Remains constant.
D
May increase or decrease, depending on the actual temperature.

Answer

Correct option: A.

Increases.

Explanation:
Temperature of a cunductor increases that causes resistivity (r) is increases & due conductivity (s) is decrease.
$\therefore\sigma=\frac{1}{\rho}$
$\Rightarrow\text{ratio of}\frac{\text{resistivity}}{\text{conductivity}}=\frac{\rho}{\sigma}=\rho^2$ is increase.

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MCQ 141 Mark

Consider a capacitor $-$ charging circuit. Let $Q_1$ be the charge given to the capacitor in a time interval of $10 ms$ and $\mathrm{Q}_2$ be the charge given in the next time interval of $10 ms$ . Let $10 mC$ charge be deposited in time interval $\mathrm{t}_1$ and another $10 mC$ charge be deposited in the next time interval $\mathrm{t}_2$.

A
$ \mathrm{Q}_1>\mathrm{Q}_2, \mathrm{t}_1>\mathrm{t}_2 $
✓
$ \mathrm{Q}_1>\mathrm{Q}_2, \mathrm{t}_1<\mathrm{t}_2$
C
$ \mathrm{Q}_1<\mathrm{Q}_2, \mathrm{t}_1>\mathrm{t}_2$
D
$ \mathrm{Q}_1<\mathrm{Q}_2, \mathrm{t}_1<\mathrm{t}_2$

Answer

Correct option: B.

$ \mathrm{Q}_1>\mathrm{Q}_2, \mathrm{t}_1<\mathrm{t}_2$

Condition for charging capacitor-
$\text{Q}=\text{Q}_0\Big(1-\text{e}^\frac{-\text{t}}{\text{Rc}}\Big)$
$\text{Q}=\text{Q}_0\Big(1-\text{e}^\frac{-10\text{m}}{\text{Rc}}\Big)\ ...(1)$
$\text{Q}_1=\text{Q}_2=\text{Q}_0\Big(1-\text{e}^\frac{{-(10\text{m}+10\text{m})}}{\text{Rc}}\Big)$
$\text{Q}_1=\text{Q}_2=\text{Q}_0\Big(1-\text{e}^\frac{{-20\text{m}}}{\text{Rc}}\Big)\ ...(2)$
From eq. $(1)$ and $(2)$ we get-
$\text{Q}_1>\text{Q}_2$
Given
$\text{Q}=\text{Q}_0\Big(1-\text{e}^\frac{-\text{t}}{\text{Rc}}\Big)$
$10\text{mc}=\text{Q}_0\Big(1-\text{e}^{\frac{-\text{t}}{\text{Rc}}}\Big)\ ...(3)$
$10\mu\text{c}+10\mu\text{c}=\text{Q}_0\Big(1-\text{e}^{\frac{-(\text{t}_1+\text{t}_2)}{\text{Rc}}}\Big)\rightarrow$
$20\mu\text{c}=\text{Q}_0\Big(1-\text{e}^{\frac{-(\text{t}_1+\text{t}_2)}{\text{Rc}}}\Big)\ ...(4)$
From eq. $(3)$ and $(4)$ we get,
$\text{t}_2>\text{t}_1$

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MCQ 151 Mark

A uniform wire of resistance $50\Omega$ is cut into 5 equal parts. These parts are now connected in parallel. The equivalent resistance of the combination is:

✓
$2\Omega$
B
$10\Omega$
C
$250\Omega$
D
$6250\Omega$

Answer

Correct option: A.

$2\Omega$

Explanation:
$\text{R}=\frac{\rho}{\text{A}}=50$

resistance of '5' equal parts are same.
$\text{R}'=\frac{\frac{\rho}{5}}{\text{A}}=\frac{50}{5}=10\Omega$
All '5' equal parts connect in parallel,

$\frac{1}{\text{R}_\text{eq}}=\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}=\frac{5}{10}$
$\text{R}_\text{eq}=2\Omega$

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MCQ 161 Mark

Two resistances R and 2R are connected in parallel in an electric circuit. The thermal energy developed in R and 2R are in the ratio:

A
1 : 2
✓
2 : 1
C
1 : 4
D
4 : 1

Answer

Correct option: B.

2 : 1

Explanation:
Thermal Energy developed $=\frac{\text{v}_2}{\text{R}}\text{t}$ (Because in Parallel, voltage is same)

$\frac{\text{Thermal Energy developedin "R"}}{\text{Thermal Energy developedin "2R"}}=\frac{\frac{\text{v}^2}{\text{R}}\text{t}}{\frac{\text{v}^2}{2\text{R}}\text{t}}=2:1$

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MCQ 171 Mark

Electrons are emitted by a hot filament and are accelerated by an electric field, as shown in the figure. The two stops at the left ensure that the electron beam has a uniform cross-section.

✓
The speed of the electrons is more at B than at A.
B
The electric current is from left to right.
C
The magnitude of the current is larger at B than at A.
D
The current density is more at B than at A.

Answer

Correct option: A.

The speed of the electrons is more at B than at A.

Explanation:
Electric field goes higher potential to Lower potential. The drift velocity of the electron at higher potentail is greater than the lower potential.
So the speed of the electron is more at B that at A.

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MCQ 181 Mark

A current passes through a resistor. Let $\mathrm{K}_1$ and $\mathrm{K}_2$ represent the average kinetic energy of the conduction electrons and the metal ions, respectively :

A
$K_2 < K_2$
B
$K_1=K_2$
✓
$\mathrm{K}_1 > \mathrm{K}_2$
D
Any of these three may occur.

Answer

Correct option: C.

$\mathrm{K}_1 > \mathrm{K}_2$

$vd$ drift velocity $=\frac{1}{2}\Big(\frac{\text{eE}}{\text{m}}\Big)\text{t}$
$\text{K.E}.=\frac{1}{2}\text{mv}^2_\text{d}=\frac{1}{2}\text{m}\Big(\frac{1}{4}\frac{\text{e}^2\text{E}^2\text{t}^2}{\text{m}^2}\Big)$
$\text{K.E}.=\frac{1}{8}\frac{\text{e}^2\text{E}^2\text{t}^2}{\text{m}}$
$\text{p}=\text{K.E}.\propto\frac{1}{\text{m}}$
Mass of electron $<$ mass of metalions.
$K.E$. of electron $> K.E$. of metalions.

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MCQ 191 Mark

The net resistance of an ammeter should be small to ensure that:

A
It does not get overheated.
B
It does not draw excessive current.
C
It can measure large currents.
✓
It does not appreciably change the current to be measured.

Answer

Correct option: D.

It does not appreciably change the current to be measured.

The net resistance of an ammeter should be small to ensure that it does not oppreciably change the current to be measured.

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Physics M.C.Q (1 Marks)

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