The steady current flows in a metallic conductor of non-uniform cross-section. The ${\rm{quantity}}\,\,{\rm{/}}\,{\rm{quantities}}$ constant along the length of the conductor ${\rm{is}}\,\,{\rm{/}}\,\,{\rm{are}}$

Current, electric field and drift velocity

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NEET • PHYSICS • CURRENT ELECTRICITY

Current electricity practice · Mixed difficulty

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Showing 1-30 of 198 questions

1 Medium

1 of 198

Understanding +4 | -1

In the absence of applied potential, the electric current flowing through a metallic wire is zero because

View answer and explanation

Correct option: C

The electrons move in random direction with a speed of the order close to that of velocity of light

Option C (The electrons move in random direction with a speed of the order close to that of velocity of light) is correct because even without an applied potential, electrons are in constant random motion due to thermal energy, with speeds close to the velocity of light, but these motions average out to zero net current.

2 Medium

2 of 198

Understanding +4 | -1

A metallic block has no potential difference applied across it, then the mean velocity of free electrons at absolute temperature

T

View answer and explanation

Correct option: C

Zero

Option C (Zero) is correct because in the absence of an applied potential difference, the free electrons move randomly, and their average velocity (mean velocity) is zero.

3 Medium

3 of 198

Understanding +4 | -1

In a thermocouple, which of the following statements is not true

View answer and explanation

Correct option: D

When the temperature of cold junction increases, the temperature of inversion also increases

Option D (When the temperature of cold junction increases, the temperature of inversion also increases) is correct because the temperature of inversion depends on the neutral temperature and the temperature of the cold junction, and the relationship is such that if the cold junction temperature increases, the temperature of inversion decreases.

4 Medium

4 of 198

Understanding +4 | -1

(A) The drift velocity of electrons decreases with the increase in the temperature of conductor.
(B) The drift velocity is inversely proportional to the area of cross-section of given conductor.
(C) The drift velocity does not depend on the applied potential difference to the conductor.
(D) The drift velocity of electron is inversely proportional to the length of the conductor.
(E) The drift velocity increases with the increase in the temperature of conductor.
Choose the correct answer from the options given below

View answer and explanation

Correct option: A

(A) and (B) only

Option A ((A) and (B) only) is correct because drift velocity decreases with increasing temperature and is inversely proportional to the cross-sectional area of the conductor.

5 Medium

5 of 198

Remembering +4 | -1

The mass of ions deposited during a given interval of time in the process of electrolysis depends on

View answer and explanation

Correct option: A

The current

Option A (The current) is correct because, according to Faraday's laws of electrolysis, the mass of ions deposited is directly proportional to the quantity of electricity (current x time) passed through the electrolyte.

6 Medium

6 of 198

Understanding +4 | -1

The steady current flows in a metallic conductor of non-uniform cross-section. The

\mathrm{quantity}\,\,\mathrm{/}\,\mathrm{quantities}

constant along the length of the conductor

\mathrm{is}\,\,\mathrm{/}\,\,\mathrm{are}

View answer and explanation

Correct option: D

Current only

Option D (Current only) is correct because in a non-uniform conductor with steady current, the current remains constant throughout the length, while the electric field and drift velocity vary due to the changing cross-sectional area.

7 Medium

7 of 198

Understanding +4 | -1

If the temperature of cold junction of thermocouple is lowered, then the neutral temperature

View answer and explanation

Correct option: D

Remains the same

Option D is correct because the neutral temperature of a thermocouple is a characteristic property of the metals used and does not depend on the cold junction temperature.

8 Medium

8 of 198

Understanding +4 | -1

For measurement of potential difference, potentiometer is preferred in comparison to voltmeter because

View answer and explanation

Correct option: D

Potentiometer does not take current from the circuit

Option D (Potentiometer does not take current from the circuit) is correct because a potentiometer works on the null deflection method, drawing no current from the source being measured.

9 Medium

9 of 198

Application +4 | -1

In a meter bridge, the gaps are closed by resistances R and S. R being less than S. A balance is obtained when the jockey makes a contact at a point 40cm from the zero end. On shunting S with a resistance of 50 ohm. The balance point moves through 10 cm. The values of R and S

View answer and explanation

Correct option: C

16.67\,\,\Omega ,\,\,25\,\Omega

Option A (Increase) is correct because when one bulb fuses, the total resistance decreases, leading to an increase in current and thus brighter illumination.

10 Medium

10 of 198

Analyzing +4 | -1

Given below are two statements:

Statement I : A uniform wire of resistance

80 \Omega

is cut into four equal parts. These parts are now connected in parallel. The equivalent resistance of the combination will be

5 \Omega

.

Statement II : Two resistances

2 R

and

3 R

are connected in parallel in a electric circuit. The value of thermal energy developed in

3 R

and

2 R

will be in the ratio

3: 2

.

In the light of the above statements, choose the most appropriate answer from the option given below.

View answer and explanation

Correct option: C

Statement I is correct but statement II is incorrect

Option C is correct. Statement I is correct as the equivalent resistance is 5 ohms. Statement II is incorrect because thermal energy is inversely proportional to resistance, so the ratio is 2:3.

11 Medium

11 of 198

Application +4 | -1

A direct current of 4A and an alternating current of 4A flows through two identical resistors. The ratio of heat produced in the two resistances in same time interval will be

View answer and explanation

Correct option: C

2\mathrm{ }:\mathrm{ }1

Option C (

2\mathrm{ }:\mathrm{ }1

) is correct because the heat produced by AC is calculated using the RMS value, which is

\frac{I}{\sqrt{2}}

, leading to half the power compared to DC.

12 Medium

12 of 198

Understanding +4 | -1

With the rise of temperature the resistivity of a semiconductor

View answer and explanation

Correct option: C

Decreases

Option C (Decreases) is correct because the resistivity of a semiconductor decreases with increasing temperature due to increased carrier concentration.

13 Easy

13 of 198

Application +4 | -1

The e.m.f. of a cell is 6 volt. When 2 ampere current is drawn from it then the potential difference across its terminals remains 3 volt. Its internal resistance wil be:

View answer and explanation

Correct option: A

1.5 \Omega

Option A (

1.5 \Omega

) is correct because the internal resistance can be calculated using the formula r = (E-V)/I.

14 Medium

14 of 198

Application +4 | -1

Two wires of the same material and equal length are joined in parallel combination. If one of them has half the thickness of the other and the thinner wire has a resistance of 8

ohms

, the resistance of the combination is equal to

View answer and explanation

Correct option: B

\frac{8}{5}\,\,ohm

Option B (

\frac{8}{5}\,ohm

) is correct because it is the equivalent resistance of the parallel combination calculated using the given resistance ratio.

15 Medium

15 of 198

Understanding +4 | -1

Given below are two statements: one is labelled as Assertion

\mathbf{A}

and the other is labelled as Reason

\mathbf{R}

.
Assertion A: Alloys such as constantan and manganin are used in making standard resistance coils.
Reason R: Constantan and manganin have very small value of temperature coefficient of resistance. In the light of the above statements, choose the correct answer from the options given below.

View answer and explanation

Correct option: A

Both

\mathbf{A}

and

\mathbf{R}

are true and

\mathbf{R}

is the correct explanation of

\mathbf{A}

Option A (Both

\mathbf{A}

and

\mathbf{R}

are true and

\mathbf{R}

is the correct explanation of

\mathbf{A}

) is correct because constantan and manganin are used in standard resistance coils precisely because they have a very small temperature coefficient of resistance, ensuring stable resistance values.

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16 Medium

16 of 198

Remembering +4 | -1

For a given thermocouple neutral temperature

View answer and explanation

Correct option: A

Is a constant

Option A (Is a constant) is correct because the neutral temperature of a thermocouple is a characteristic constant for a given pair of metals.

17 Medium

17 of 198

Application +4 | -1

A resistor has a colour code of green, blue, brown and silver. What is its resistance?

View answer and explanation

Correct option: C

560\,\,\mathrm{\Omega }\,\, \pm \,\,10\,\,\mathrm{\% }

Option C (

560\,\mathrm{\Omega }\,\, \pm \,\,10\,\mathrm{\% }

) is correct because green is 5, blue is 6, brown is a multiplier of 10¹, and silver is a tolerance of 10%.

18 Easy

18 of 198

Application +4 | -1

The emf of a battery A is balanced by a length of 80 cm on a potentiometer wire. The emf of a standard cell 1 V is balanced by 50 cm. The emf of A is

View answer and explanation

Correct option: D

1.6 V

Option D (1.6 V) is correct because the emf is directly proportional to the balancing length in a potentiometer experiment.

19 Hard

19 of 198

Application +4 | -1

Resistance of a wire at

20\,\,{\,^0}C

20\,\,\,\Omega

and at

500\,\,{\,^0}C

C is

60\,\,\,\Omega

. At what temperature its resistance is

25\,\,\,\Omega

View answer and explanation

Correct option: D

80\,{\,^0}\mathrm{C}

Option D (

80\,{\,^0}\mathrm{C}

) is correct because it is the temperature calculated using the linear relationship between resistance and temperature.

20 Medium

20 of 198

Application +4 | -1

The length of a potentiometer wire is

l

. A cell of emf E is balanced at a length

l/4

from the positive end of the wire. If the length of the wire is increased by

l/2

, at what distance will the same cell give a balanced point? (Potentiometer battery is ideal)

View answer and explanation

Correct option: B

\frac{{3l}}{8}

Option A (

25\mathrm{ }watt

bulb) is correct because in a series connection, the bulb with higher resistance will dissipate more power and glow brighter.

21 Medium

21 of 198

Analyzing +4 | -1

Assertion: Terminal potential difference of a cell is always less than its emf.
Reason: Potential drop due to internal resistance of cell increases the terminal potential difference.

View answer and explanation

Correct option: D

If both Assertion & Reason are False

Option D (If both Assertion & Reason are False) is correct because the terminal potential difference is usually *less* than the EMF due to internal resistance, and the potential drop *decreases* the terminal potential difference.

22 Easy

22 of 198

Application +4 | -1

When a current

I

is set up in a wire of radius

r

, the drift velocity is

\mathrm{v}_{\mathrm{d}}

. If the same current is set up through a wire of radius

2 \mathrm{r}

, the drift velocity will be

View answer and explanation

Correct option: D

\mathrm{v}_{\mathrm{d}} / 4

Option D (

\mathrm{v}_{\mathrm{d}} / 4

) is correct because the drift velocity is inversely proportional to the cross-sectional area of the wire, which is proportional to the square of the radius.

23 Medium

23 of 198

Understanding +4 | -1

For comparing the e.m.f.'s of two cells with a potentiometer, a standard cell is used to develop a potential gradient along the wires. Which of the following possibilities would make the experiment unsuccessful

View answer and explanation

Correct option: D

The e.m.f. of the standard cell is smaller than the e.m.f.'s of the two cells

Option D (The e.m.f. of the standard cell is smaller than the e.m.f.'s of the two cells) is correct because the potential gradient developed must be higher than the emf of the cells being compared for a balance point to be obtained.

24 Medium

24 of 198

Understanding +4 | -1

The potentiometer is superior to a voltmeter for measuring a potential difference because

View answer and explanation

Correct option: B

The potentiometer does not draw any current from the source of the potential

Option B (The potentiometer does not draw any current from the source of the potential) is correct because the potentiometer uses a null method, ensuring no current is drawn from the source, leading to a more accurate measurement.

25 Medium

25 of 198

Remembering +4 | -1

In a thermocouple, the temperature that does not depend on the temperature of the cold junction is called

View answer and explanation

Correct option: A

Neutral temperature

The neutral temperature in a thermocouple does not depend on the temperature of the cold junction. It is a characteristic of the thermocouple materials.

26 Medium

26 of 198

Understanding +4 | -1

A current

I

is passed for a time

t

through a number of voltmeters. If

m

is the mass of a substance deposited on an electrode and

z

is its electrochemical equivalent, then

View answer and explanation

Correct option: A

\frac{{zIt}}{m} = \mathrm{constant}

Option A (

\frac{{zIt}}{m} = \mathrm{constant}

) is correct because Faraday's law of electrolysis states that the mass of a substance deposited is directly proportional to the charge (It) and the electrochemical equivalent (z).

27 Medium

27 of 198

Understanding +4 | -1

Two bulbs, one of

50\,\,watt

and another of

25\,\,watt

are connected in series to the mains. The ratio of the currents through them is

View answer and explanation

Correct option: C

\begin{array}{llllllllllllllllllll} {\mathrm{1 :1}} \end{array}

Option C (1:1) is correct because when bulbs are connected in series, the current flowing through each bulb is the same, regardless of their power ratings.

28 Medium

28 of 198

Remembering +4 | -1

Ampere hour is the unit of

View answer and explanation

Correct option: A

Quantity of charges

Option A (Quantity of charges) is correct because Ampere-hour (Ah) is a unit of electric charge, representing the amount of charge transferred by a current of one ampere flowing for one hour.

29 Medium

29 of 198

Understanding +4 | -1

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

View answer and explanation

Correct option: B

Increase

Option B (Increase) is correct because decreasing the number of collisions reduces resistance, leading to an increase in current according to Ohm's Law.

30 Easy

30 of 198

Application +4 | -1

The radius

(r)

, length

(l)

and resistance

(R)

of a metal wire was measured in the laboratory as

r=(0.35 \pm 0.05) \mathrm{cm}

R=(100 \pm 10) \mathrm{ohm}

l=(15 \pm 0.2) \mathrm{cm}

The percentage error in resistivity of the material of the wire is:

View answer and explanation

Correct option: B

39.9 \%

Option B (

39.9 \%

) is correct because it is the percentage error in resistivity calculated using the given errors in radius, length, and resistance.

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Key Takeaways

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