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MCQOPTIONS
This section includes 12583 Mcqs, each offering curated multiple-choice questions to sharpen your Joint Entrance Exam - Main (JEE Main) knowledge and support exam preparation. Choose a topic below to get started.
| 7451. |
An electric wire of length ?I? and area of cross-section \[a\] has a resistance R ohms. Another wire of the same material having same length and area of cross-section 4a has a resistance of [MP PMT 1993] |
| A. | 4R |
| B. | R/4 |
| C. | R/16 |
| D. | 16R |
| Answer» C. R/16 | |
| 7452. |
The resistances of a wire at temperatures \[t{}^\circ C\] and \[0{}^\circ C\] are related by [MP PMT 1993] |
| A. | \[{{R}_{t}}={{R}_{0}}(1+\alpha \,t)\] |
| B. | \[{{R}_{t}}={{R}_{0}}(1-\alpha \,t)\] |
| C. | \[{{R}_{t}}=R_{0}^{2}(1+\alpha \,t)\] |
| D. | \[{{R}_{t}}=R_{0}^{2}(1-\alpha \,t)\] |
| Answer» B. \[{{R}_{t}}={{R}_{0}}(1-\alpha \,t)\] | |
| 7453. |
An electric wire is connected across a cell of e.m.f. E. The current \[I\] is measured by an ammeter of resistance R. According to ohm's law [MP PMT 1993] |
| A. | \[E={{I}^{2}}R\] |
| B. | \[E=IR\] |
| C. | \[E=R/I\] |
| D. | \[E=I/R\] |
| Answer» C. \[E=R/I\] | |
| 7454. |
Two wires of the same material are given. The first wire is twice as long as the second and has twice the diameter of the second. The resistance of the first will be [MP PMT 1993] |
| A. | Twice of the second |
| B. | Half of the second |
| C. | Equal to the second |
| D. | Four times of the second |
| Answer» C. Equal to the second | |
| 7455. |
5 amperes of current is passed through a metallic conductor. The charge flowing in one minute in coulombs will be [MP PET 1984] |
| A. | 5 |
| B. | 12 |
| C. | 1/12 |
| D. | 300 |
| Answer» E. | |
| 7456. |
Every atom makes one free electron in copper. If 1.1 ampere current is flowing in the wire of copper having 1 mm diameter, then the drift velocity (approx.) will be (Density of copper \[=9\times {{10}^{3}}\,kg\,{{m}^{-3}}\] and atomic weight = 63) [CPMT 1989] |
| A. | \[0.3\,mm/\sec \] |
| B. | \[0.1\,mm/\sec \] |
| C. | \[0.2\,mm/\sec \] |
| D. | \[0.2\,cm/\sec \] |
| Answer» C. \[0.2\,mm/\sec \] | |
| 7457. |
It is easier to start a car engine on a hot day than on a cold day. This is because the internal resistance of the car battery |
| A. | Decreases with rise in temperature |
| B. | Increases with rise in temperature |
| C. | Decreases with a fall in temperature |
| D. | Does not change with a change in temperature |
| Answer» B. Increases with rise in temperature | |
| 7458. |
There is a current of 1.344 amp in a copper wire whose area of cross-section normal to the length of the wire is 1\[m{{m}^{2}}\]. If the number of free electrons per \[c{{m}^{3}}\] is \[8.4\times {{10}^{22}}\], then the drift velocity would be [CPMT 1990] |
| A. | 1.0\[mm/sec\] |
| B. | 1.0\[m/sec\] |
| C. | 0.1\[mm/sec\] |
| D. | 0.01\[mm/sec\] |
| Answer» D. 0.01\[mm/sec\] | |
| 7459. |
The resistance of a wire of uniform diameter \[d\] and length \[L\] is \[R\]. The resistance of another wire of the same material but diameter \[2d\] and length \[4L\] will be [CPMT 1984; MP PET 2002] |
| A. | \[2R\] |
| B. | \[R\] |
| C. | \[R/2\] |
| D. | \[R/4\] |
| Answer» C. \[R/2\] | |
| 7460. |
There is a current of 20 amperes in a copper wire of \[{{10}^{-6}}\] square metre area of cross-section. If the number of free electrons per cubic metre is \[{{10}^{29}}\], then the drift velocity is |
| A. | \[125\times {{10}^{-3}}m/sec\] |
| B. | \[12.5\times {{10}^{-3}}m/sec\] |
| C. | \[1.25\times {{10}^{-3}}m/sec\] |
| D. | \[1.25\times {{10}^{-4}}m/sec\] |
| Answer» D. \[1.25\times {{10}^{-4}}m/sec\] | |
| 7461. |
In the above question, the resistance between the square faces is [MP PET 1993] |
| A. | \[3\times {{10}^{-9}}ohm\] |
| B. | \[3\times {{10}^{-7}}ohm\] |
| C. | \[3\times {{10}^{-5}}ohm\] |
| D. | \[3\times {{10}^{-3}}ohm\] |
| Answer» E. | |
| 7462. |
Dimensions of a block are \[1\,cm\times 1\,cm\times 100\,cm\]. If specific resistance of its material is \[3\times {{10}^{-7}}ohm-m\], then the resistance between the opposite rectangular faces is [MP PET 1993] |
| A. | \[3\times {{10}^{-9}}ohm\] |
| B. | \[3\times {{10}^{-7}}ohm\] |
| C. | \[3\times {{10}^{-5}}ohm\] |
| D. | \[3\times {{10}^{-3}}ohm\] |
| Answer» C. \[3\times {{10}^{-5}}ohm\] | |
| 7463. |
The fact that the conductance of some metals rises to infinity at some temperature below a few Kelvin is called |
| A. | Thermal conductivity |
| B. | Optical conductivity |
| C. | Magnetic conductivity |
| D. | Superconductivity |
| Answer» E. | |
| 7464. |
When current flows through a conductor, then the order of drift velocity of electrons will be [CPMT 1986] |
| A. | \[{{10}^{10}}\,m/\sec \] |
| B. | \[{{10}^{-2}}\,cm/\sec \] |
| C. | \[{{10}^{4}}\,cm/\sec \] |
| D. | \[{{10}^{-1}}\,cm/\sec \] |
| Answer» C. \[{{10}^{4}}\,cm/\sec \] | |
| 7465. |
A metallic block has no potential difference applied across it, then the mean velocity of free electrons is \[T\] = absolute temperature of the block) |
| A. | Proportional to \[T\] |
| B. | Proportional to \[\sqrt{T}\] |
| C. | Zero |
| D. | Finite but independent of temperature |
| Answer» C. Zero | |
| 7466. |
Through a semiconductor, an electric current is due to drift of |
| A. | Free electrons |
| B. | Free electrons and holes |
| C. | Positive and negative ions |
| D. | Protons |
| Answer» C. Positive and negative ions | |
| 7467. |
A wire of length 5\[m\] and radius 1\[mm\] has a resistance of 1 ohm. What length of the wire of the same material at the same temperature and of radius 2\[mm\] will also have a resistance of 1 ohm |
| A. | 1.25\[m\] |
| B. | 2.5\[m\] |
| C. | 10\[m\] |
| D. | 20\[m\] |
| Answer» E. | |
| 7468. |
In hydrogen atom, the electron makes \[6.6\times {{10}^{15}}\] revolutions per second around the nucleus in an orbit of radius \[0.5\times {{10}^{-10}}m\]. It is equivalent to a current nearly |
| A. | 1 A |
| B. | 1 mA |
| C. | \[1\,\mu A\] |
| D. | \[1.6\times {{10}^{-19}}A\] |
| Answer» C. \[1\,\mu A\] | |
| 7469. |
A certain wire has a resistance \[R\]. The resistance of another wire identical with the first except having twice its diameter is [CPMT 1999] |
| A. | \[2\,R\] |
| B. | \[0.25\,R\] |
| C. | \[4\,R\] |
| D. | \[0.5\,R\] |
| Answer» C. \[4\,R\] | |
| 7470. |
A wire 100\[cm\] long and 2.0\[mm\] diameter has a resistance of 0.7 ohm, the electrical resistivity of the material is |
| A. | \[4.4\times {{10}^{-6}}ohm\times m\] |
| B. | \[2.2\times {{10}^{-6}}ohm\times m\] |
| C. | \[1.1\times {{10}^{-6}}ohm\times m\] |
| D. | \[0.22\times {{10}^{-6}}ohm\times m\] |
| Answer» C. \[1.1\times {{10}^{-6}}ohm\times m\] | |
| 7471. |
When a piece of aluminium wire of finite length is drawn through a series of dies to reduce its diameter to half its original value, its resistance will become [NCERT 1974; AIIMS 1997; MH CET 2000; UPSEAT 2001; CBSE PMT 2002] |
| A. | Two times |
| B. | Four times |
| C. | Eight times |
| D. | Sixteen times |
| Answer» E. | |
| 7472. |
A piece of wire of resistance 4 ohms is bent through \[180{}^\circ \] at its mid-point and the two halves are twisted together, then the resistance is [CPMT 1971] |
| A. | 8 ohms |
| B. | 1 ohm |
| C. | 2 ohms |
| D. | 5 ohms |
| Answer» C. 2 ohms | |
| 7473. |
\[62.5\times {{10}^{18}}\] electrons per second are flowing through a wire of area of cross-section 0.1\[{{m}^{2}}\], the value of current flowing will be [CPMT 1984] |
| A. | 1 A |
| B. | 0.1 A |
| C. | 10 A |
| D. | 0.11 A |
| Answer» D. 0.11 A | |
| 7474. |
The specific resistance of a wire is \[\rho \], its volume is 3\[{{m}^{3}}\] and its resistance is 3 ohms, then its length will be [CPMT 1984] |
| A. | \[\sqrt{\frac{1}{\rho }}\] |
| B. | \[\frac{3}{\sqrt{\rho }}\] |
| C. | \[\frac{1}{\rho }\sqrt{3}\] |
| D. | \[\rho \sqrt{\frac{1}{3}}\] |
| Answer» C. \[\frac{1}{\rho }\sqrt{3}\] | |
| 7475. |
In a conductor 4 coulombs of charge flows for 2 seconds. The value of electric current will be [CPMT 1984] |
| A. | 4 volts |
| B. | 4 amperes |
| C. | 2 amperes |
| D. | 2 volts |
| Answer» D. 2 volts | |
| 7476. |
On increasing the temperature of a conductor, its resistance increases because [CPMT 1982] |
| A. | Relaxation time decreases |
| B. | Mass of the electrons increases |
| C. | Electron density decreases |
| D. | None of the above |
| Answer» B. Mass of the electrons increases | |
| 7477. |
The example for non-ohmic resistance is [MP PMT 1978] |
| A. | Copper wire |
| B. | Carbon resistance |
| C. | Diode |
| D. | Tungston wire |
| Answer» D. Tungston wire | |
| 7478. |
Drift velocity \[{{v}_{d}}\] varies with the intensity of electric field as per the relation [CPMT 1981; BVP 2003] |
| A. | \[{{v}_{d}}\propto E\] |
| B. | \[{{v}_{d}}\propto \frac{1}{E}\] |
| C. | \[{{v}_{d}}=\text{constant}\] |
| D. | \[{{v}_{d}}\propto {{E}^{2}}\] |
| Answer» B. \[{{v}_{d}}\propto \frac{1}{E}\] | |
| 7479. |
Two wires that are made up of two different materials whose specific resistance are in the ratio 2 : 3, length 3 : 4 and area 4 : 5. The ratio of their resistances is [Kerala PMT 2005] |
| A. | 6 : 5 |
| B. | 6 : 8 |
| C. | 5 : 8 |
| D. | 1 : 2 |
| Answer» D. 1 : 2 | |
| 7480. |
The electric field E, current density J and conductivity s of a conductor are related as [Kerala PMT 2005] |
| A. | \[\sigma =E/j\] |
| B. | \[\sigma =j/E\] |
| C. | \[\sigma =jE\] |
| D. | \[\sigma =1/jE\] |
| Answer» C. \[\sigma =jE\] | |
| 7481. |
The length of the resistance wire is increased by 10%. What is the corresponding change in the resistance of wire [MH CET 2004] |
| A. | 10% |
| B. | 25% |
| C. | 21% |
| D. | 9% |
| Answer» D. 9% | |
| 7482. |
A thick wire is stretched so that its length become two times. Assuming that there is no change in its density, then what is the ratio of change in resistance of wire to the initial resistance of wire [MH CET 2004] |
| A. | 2 : 1 |
| B. | 4 : 1 |
| C. | 3 : 1 |
| D. | 1 : 4 |
| Answer» D. 1 : 4 | |
| 7483. |
The colour sequence in a carbon resistor is red, brown, orange and silver. The resistance of the resistor is [DCE 2004] |
| A. | \[21\times {{10}^{3}}\pm 10%\] |
| B. | \[23\times {{10}^{1}}\pm 10\] |
| C. | \[21\times {{10}^{3}}\pm 5%\] |
| D. | \[12\times {{10}^{3}}\pm 5%\] |
| Answer» B. \[23\times {{10}^{1}}\pm 10\] | |
| 7484. |
The following four wires are made of the same material and are at the same temperature. Which one of them has highest electrical resistance [UPSEAT 2004] |
| A. | Length = 50 cm, diameter = 0.5 mm |
| B. | Length = 100 cm, diameter = 1 mm |
| C. | Length = 200 cm, diameter = 2 mm |
| D. | Length = 300 cm, diameter = 3 mm |
| Answer» B. Length = 100 cm, diameter = 1 mm | |
| 7485. |
The electric resistance of a certain wire of iron is R. If its length and radius are both doubled, then [CBSE PMT 2004] |
| A. | The resistance will be doubled and the specific resistance will be halved |
| B. | The resistance will be halved and the specific resistance will remain unchanged |
| C. | The resistance will be halved and the specific resistance will be doubled |
| D. | The resistance and the specific resistance, will both remain unchanged |
| Answer» C. The resistance will be halved and the specific resistance will be doubled | |
| 7486. |
When a potential difference is applied across the ends of a linear metallic conductor [MP PET 1997] |
| A. | The free electrons are accelerated continuously from the lower potential end to the higher potential end of the conductor |
| B. | The free electrons are accelerated continuously from the higher potential end to the lower potential end of the conductor |
| C. | The free electrons acquire a constant drift velocity from the lower potential end to the higher potential end of the conductor |
| D. | The free electrons are set in motion from their position of rest |
| Answer» D. The free electrons are set in motion from their position of rest | |
| 7487. |
The alloys constantan and managing are used to make standard resistance due to they have [MH CET 2000; NCERT 1990] |
| A. | Low resistivity |
| B. | High resistivity |
| C. | Low temperature coefficient of resistance |
| D. | Both B and C |
| Answer» E. | |
| 7488. |
The lead wires should have [Pb. PMT 2000] |
| A. | Larger diameter and low resistance |
| B. | Smaller diameter and high resistance |
| C. | Smaller diameter and low resistance |
| D. | Larger diameter and high resistance |
| Answer» B. Smaller diameter and high resistance | |
| 7489. |
What is the resistance of a carbon resistance which has bands of colours brown, black and brown [DCE 1999] |
| A. | 100 W |
| B. | 1000 W |
| C. | 10 W |
| D. | 1 W |
| Answer» B. 1000 W | |
| 7490. |
A resistance R is stretched to four times its length. Its new resistance will be [ISM Dhanbad 1994; UPSEAT 2003] |
| A. | 4 R |
| B. | 64 R |
| C. | \[R/4\] |
| D. | 16 R |
| Answer» E. | |
| 7491. |
The new resistance of wire of R W, whose radius is reduced half, is [J & K CET 2004; Pb PMT 2004] |
| A. | 16 R |
| B. | 3 R |
| C. | 2R |
| D. | R |
| Answer» B. 3 R | |
| 7492. |
The resistivity of a wire [MP PMT 1984; DPMT 1982] |
| A. | Increases with the length of the wire |
| B. | Decreases with the area of cross-section |
| C. | Decreases with the length and increases with the cross-section of wire |
| D. | None of the above statement is correct |
| Answer» E. | |
| 7493. |
A source of e.m.f. E = 15 V and having negligible internal resistance is connected to a variable resistance so that the current in the circuit increases with time as i = 1.2 t + 3. Then, the total charge that will flow in first five second will be [Kerala PMT 2004; J & K CET 2004] |
| A. | 10 C |
| B. | 20 C |
| C. | 30 C |
| D. | 40 C |
| Answer» D. 40 C | |
| 7494. |
The length of the wire is doubled. Its conductance will be [Kerala PMT 2004] |
| A. | Unchanged |
| B. | Halved |
| C. | Quadrupled |
| D. | 1/4 of the original value |
| Answer» C. Quadrupled | |
| 7495. |
In a hydrogen discharge tube it is observed that through a given cross-section \[3.13\times {{10}^{15}}\] electrons are moving from right to left and \[3.12\times {{10}^{15}}\] protons are moving from left to right. What is the electric current in the discharge tube and what is its direction [AFMC 1996] |
| A. | \[1\,mA\,\]towards right |
| B. | \[1mA\] towards left |
| C. | \[2mA\] towards left |
| D. | \[2\,mA\] towards right |
| Answer» B. \[1mA\] towards left | |
| 7496. |
We have two wires A and B of same mass and same material. The diameter of the wire A is half of that B. If the resistance of wire A is 24 ohm then the resistance of wire B will be [CPMT 2003] |
| A. | 12 Ohm |
| B. | 3.0 Ohm |
| C. | 1.5 Ohm |
| D. | None of the above |
| Answer» D. None of the above | |
| 7497. |
The length of a given cylindrical wire is increased by 100 %. Due to the consequent decrease in diameter the change in the resistance of the wire will be [AIEEE 2003] |
| A. | 300 % |
| B. | 200 % |
| C. | 100 % |
| D. | 50 % |
| Answer» B. 200 % | |
| 7498. |
A strip of copper and another of germanium are cooled from room temperature to 80 K. The resistance of [AIEEE 2003] |
| A. | Each of these increases |
| B. | Each of these decreases |
| C. | Copper strip increases and that of germanium decreases |
| D. | Copper strip decreases and that of germanium increases |
| Answer» E. | |
| 7499. |
What length of the wire of specific resistance \[48\times {{10}^{-8}}\,\Omega \,\,m\] is needed to make a resistance of 4.2 W (diameter of wire = 0.4 mm) [CBSE PMT 2000; Pb. PMT 2002] |
| A. | 4.1 m |
| B. | 3.1 m |
| C. | 2.1 m |
| D. | 1.1 m |
| Answer» E. | |
| 7500. |
When a current flows through a conductor its temperature [MHCET 2002] |
| A. | May increase or decrease |
| B. | Remains same |
| C. | Decreases |
| D. | Increases |
| Answer» E. | |