Unit of Current Important Questions

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Unit of Current is Ampere. It is denoted by the symbol A. It is also denoted by the shorted form ‘amps’. One ampere is equal to 6.241509074 × 1018 electrons worth of charge moving past a point in a second. The charge of an electron e is 1.602 176634 ×10-19 Coulomb. Unit of current is an SI unit and thus used universally for all current measurements. This topic is under Class 12 Chapter 3 Current Electricity

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Important Questions on Unit of Current

Ques 1. Define Ampere. (2 marks)

Ans. Ampere is the flow of electric charge at the rate of 1 coulomb per second. Ampere is denoted by the symbol A.

Ques 2. What are the uses of Ammeter? (2 marks)

Ans. Ammeter is a device used to measure electric current. It can measure both alternating current and direct current. It is connected in series inorder to measure the current.

Ques 3. Calculate the resistance of a light bulb if its voltage is 10V and carries a current 5A. (3 marks)

Ans: By Ohm’s law,

V = IR

R = V/I

R =10/5

R = 2 Ohms

Ques 4. A battery connected to a 0.8 amp light bulb can effectively store 5,500 C of charge when fully charged. How long will the battery last before going dead if the light is left on? (3 marks)

Ans. We know that

I = Q/t

t = Q/I

= 5500/0.8

= 6875 sec

= 1.91 hours

Ques 5. A light bulb draws 300mA of current when its voltage is 240V. Calculate the resistance. (3 marks)

Ans. I = 300mA = 300/1000 A

= 0.3 A

V = 240V

By Ohm’s law,

V = IR

R = V/I

R = 240/0.3

R = 800 Ohms

Ques 6. Calculate the current passing through an electrical device of resistance 10 ohms and voltage 100V. (3 marks)

Ans. R = 10 ohms

V = 100V

By Ohm’s law,

V = IR

I = V/R

= 100/10

= 10 Ampere

Ques 7. What is electric current? (2 marks)

Ans. The rate of flow of charges through a conductor with a defined potential difference is called electric current. If Q is the charge flowing through a conductor in a time interval of t, then current I is given by,

I = Q/t

Ques 8. If current flowing through a conductor for 6 minutes id 0.6A, find the charge. (3 marks)

Ans. We know that,

I = Q/t

Q = ?

I = 0.6A

t = 6 min = 360 sec

Q = Ixt

= 0.6 x 360

= 216 C

Ques 9. If 2A current flows for 5 minutes, the amount of charge flowing through the conductor is? (3 marks)

Ans. We know that,

I = Q/t

I = 2A

t = 5 min = 300 sec

Q = Ixt

= 2 x 300

= 600C

Ques 10. If 600C charge flows for 5 minutes, calculate the current flowing through the conductor.  (3 marks)

Ans. We know that,

I = Q/t

I = ?

Q = 600C

t = 5 min = 300 sec

I = Q/t

= 600/300

= 2A

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CBSE CLASS XII Related Questions

  • 1.
    If Bohr’s quantization postulate (angular momentum \( = \frac{nh}{2\pi} \)) is a basic law of nature, it should be equally valid for the case of planetary motion also. Why, then, do we never speak of quantization of orbits of planets around the Sun? Explain.


      • 2.
        Draw a circuit diagram of a full-wave rectifier using p-n junction diodes. Explain its working and show the input-output waveforms.


          • 3.
            Two small identical metallic balls having charges \( q \) and \( -2q \) are kept far at a separation \( r \). They are brought in contact and then separated at distance \( \frac{r}{2} \). Compared to the initial force \( F \), they will now:

              • attract with a force \( \frac{F}{2} \)
              • repel with a force \( \frac{F}{2} \)
              • repel with a force \( F \)
              • attract with a force \( F \)

            • 4.
              Two parallel plate capacitors X and Y are connected in series to a 6 V battery. They have the same plate area and same plate separation but capacitor X has air between its plates, whereas capacitor Y contains a material of dielectric constant 4. Calculate the capacitances of X and Y, if the equivalent capacitance of the combination of X and Y is \( 4 \, \mu\text{F} \). Calculate the potential difference across the plates of X and Y.


                • 5.
                  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° in 0.2 s. The value of emf induced in the loop will be:

                    • 5 V
                    • 3.5 V
                    • 2.5 V
                    • Zero V

                  • 6.
                    Assertion (A) : The mass of a nucleus is less than the sum of the masses of the constituent nucleons. Reason (R) : Energy is absorbed when the nucleons are bound together to form a nucleus.

                      • Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
                      • Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
                      • Assertion (A) is true, but Reason (R) is false.
                      • Both Assertion (A) and Reason (R) are false.
                    CBSE CLASS XII Previous Year Papers

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