Unit of Current MCQs

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Unit of Current is Ampere. Ampere is the SI unit of current. It forms one of the fundamental units of physical quantities. Ampere is denoted by A. Electric current is the rate of flow of charge. The value of the charge of an electron e is 1.602 x 176634 ×10^-19. Unit of current is very important to know to solve problems related to Current Electricity.

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MCQs on Unit of Current

Ques 1. What is the unit of current?

Ampere
Volt
Ohm
Watt

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Answer: a

Explanation: SI unit of electric current is Ampere. Ampere is the flow of electric charge at the rate of 1 coulomb per second. Ampere is denoted by the symbol A. Electric current is measured by a device called Ammeter.

Ques 2. Electric pressure is also called?

Resistance
Voltage
Wattage
Power

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Answer: b

Explanation: Voltage is defined as the work needed per unit of charge to move a test charge between the two points. It is also called electric potential difference, electric pressure or electric tension is the difference in electric potential between two points.

Ques 3. Materials that offer less resistance and enables free movement of electrons is called?

Conductors
Insulators
Semiconductor
Inductors

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Answer: a

Explanation: Conductors are materials that have free electrons which enables them to conduct electricity.

Ques 4. Which one is a poor conductor of electricity?

Iron
Silver
Wood
Tungsten

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Answer: c

Explanation: Wood is a non-conductive material and thus acts as an insulator. Most of the metals are very good conductors of electricity.

Ques 5. The property by which a material allows current to pass through it is called?

Resistance
Reactance
Capacitance
Conductance

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Answer: d

Explanation: Conductance is the property of a material to conduct electricity. Conductivity is amount or effective current a material can conduct. It is denoted by σ.

Ques 6. Conductance is the reciprocal of?

Resistance
Reactance
Capacitance
Conductance

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Answer: a

Explanation: Conductance is the property of a material to conduct electricity. On the other hand, resistance is the property of a material to resist the electric current from passing through it.

Ques 7. Resistance varies inversely with?

Length
Cross section
Temperature
Resistivity

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Answer: b

Explanation: Resistance is directly proportional to resistivity and length. It is inversely proportional to cross sectional area of the conductor.

R = $\frac{pL}{A}$ p = resistivity, L = length, A = cross sectional area

Ques 8. Which instrument is used to detect electric current?

Galvanometer
Wattmeter
Rheostat
Voltmeter

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Answer: a

Explanation: Galvanometer is a device used to measure electric current and intensity. It is indicated by a magnetic needle's movement or that of a coil in a magnetic field. A galvanometer is also used as an ammeter and a voltmeter.

Ques 9. Calculate the voltage across a 33 ohm resistor carrying 2A current.

33V
46V
66V
99V

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Answer: c

Explanation: By Ohm’s law,

V = IR

V = 2 x 33

V = 66 volts

Ques 10. Calculate the resistance of a light bulb if its voltage is 5V and carries a current 10A.

0.2 Ohms
0.1 Ohms
0.5 Ohms
2 Ohms

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Answer: c

Explanation: By Ohm’s law,

V = IR

R = V/I

R = 5/10

R = 0.5 Ohms

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CBSE CLASS XII Related Questions

1.
A current of $4.0\,\text{A}$ flows through a wire of length $1\,\text{m}$ and cross-sectional area $1.0\,\text{mm}^2$, when a potential difference of $2\,\text{V}$ is applied across its ends. Calculate the resistivity of the material of the wire.
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2.
In a region, the electric potential varies as $V = 10 - 50x$, where $V$ is in volts and $x$ is in meters. The electric field in the region is
- $10\ \text{N/C}$ along $+x$
- $10\ \text{N/C}$ along $-x$
- $50\ \text{N/C}$ along $+x$
- $50\ \text{N/C}$ along $-x$
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3.
A wire of length $L$ is bent round into (i) a square coil having $N$ turns and (ii) a circular coil having $N$ turns. The coil in both cases is free to turn about a vertical axis coinciding with the plane of the coil, in a uniform, horizontal magnetic field and carry the same currents. Find the ratio of the maximum value of the torque acting on the square coil to that on the circular coil.
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4.
A circular coil of 100 turns and radius $\left(\frac{10}{\sqrt{\pi}}\right)$ cm carrying current of $5.0\,\text{A}$ is suspended vertically in a uniform horizontal magnetic field of $2.0\,\text{T}$. The field makes an angle $30^\circ$ with the normal to the coil. Calculate:
(I) the magnetic dipole moment of the coil, and
(II) the magnitude of the counter torque that must be applied to prevent the coil from turning.
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5.
A magnet held vertically, with its north pole down, is dropped along the axis of a closed solenoid placed vertically on a table. If the observer looks down from the top,
- the induced current will flow in the anticlockwise direction.
- the induced current will flow in the clockwise direction.
- no induced current will flow in the solenoid.
- the magnet will fall with a constant velocity.
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6.
A square loop of side 0.50 m is placed in a uniform magnetic field of 0.4 T perpendicular to the plane of the loop. The loop is rotated through an angle of $60^\circ$ in 0.2 s. The value of emf induced in the loop will be:
- 5 V
- 3.5 V
- 2.5 V
- Zero V
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