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?

  1. Ampere
  2. Volt
  3. Ohm
  4. 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?

  1. Resistance
  2. Voltage
  3. Wattage
  4. 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?

  1. Conductors
  2. Insulators
  3. Semiconductor
  4. 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?

  1. Iron
  2. Silver
  3. Wood
  4. 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?

  1. Resistance
  2. Reactance
  3. Capacitance
  4. 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?

  1. Resistance
  2. Reactance
  3. Capacitance
  4. 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?

  1. Length
  2. Cross section
  3. Temperature
  4. 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?

  1. Galvanometer
  2. Wattmeter
  3. Rheostat
  4. 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.

  1. 33V
  2. 46V
  3. 66V
  4. 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.

  1. 0.2 Ohms
  2. 0.1 Ohms
  3. 0.5 Ohms
  4. 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.

    Assertion (A): The deflection in a galvanometer is directly proportional to the current passing through it. 

    Reason (R): The coil of a galvanometer is suspended in a uniform radial magnetic field.

      • Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A)
      • Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
      • Assertion (A) is true, but Reason (R) is false.
      • Assertion (A) is false and Reason (R) is also false.

    • 2.
      A current carrying circular loop of area A produces a magnetic field \( B \) at its centre. Show that the magnetic moment of the loop is \( \frac{2BA}{\mu_0} \sqrt{\frac{A}{\pi}} \).


        • 3.
          An electron in Bohr model of hydrogen atom makes a transition from energy level \(-1.51 \, \text{eV}\) to \(-3.40 \, \text{eV}\). Calculate the change in the radius of its orbit. The radius of orbit of electron in its ground state is \(0.53 \, \text{\AA}\).


            • 4.
              The electric field (\( \vec{E} \)) and electric potential (\( V \)) at a point inside a charged hollow metallic sphere are respectively:

                • \( E = 0, \quad V = 0 \)
                • \( E = 0, \quad V = V_0 \text{ (a constant)} \)
                • \( E \ne 0, \quad V \ne 0 \)
                • \( E = E_0 \text{ (a constant)}, \quad V = 0 \)

              • 5.

                Two slits 0.1 mm apart are arranged 1.20 m from a screen. Light of wavelength 600 nm from a distant source is incident on the slits. How far apart will adjacent bright interference fringes be on the screen? 


                  • 6.
                    In the given figure, three identical bulbs P, Q, and S are connected to a battery.
                    three identical bulbs P, Q, and S

                    [(i)] Compare the brightness of bulbs P and Q with that of bulb S when key K is closed.

                    [(ii)] Compare the brightness of the bulbs S and Q when the key K is opened.
                    Justify your answer in both cases.

                      CBSE CLASS XII Previous Year Papers

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