Unit of Electric Charge: Definition, Properties, Formula & Sample Questions

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Jasmine Grover

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Unit of Electric charge is Coulomb. Electric Charge is a property of matter as a result of which, the matter experiences a force when it is placed in an electromagnetic field. Objects are either attracted to or repelled from one another due to electric charge. Positive and negative charges are the two sorts of charges. The electric charge is the amount of charge flowing through a specific location at a specific time. 

Key Words: Electric Charge, Electromagnetic field, Electrons, Protons, Coulomb’s law, Electricity, Matter, Coulomb, Ampere, Mass, Length, Time


SI Unit of Electric Charge

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The SI unit of electric charge is Coulomb, represented by C. When a current of one Ampere travels across a unit cross-sectional area for one second, the charge is said to be one coulomb. A particle's charge is essentially the sum of the charges of all the electrons in it. It can be represented as-

q = ne

where q = charge, 

n = number of electrons, 

and e = charge on 1 electron = 1.6 x 10-19 C

Furthermore, the CGS unit of electric charge is a composite of three fundamental quantities: mass, length, and time.


Other units of Electric Charge

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The other units of electric charge used to measure it are as follows – 

Unit Name Unit Symbol
abCoulomb  abC
statCoulomb statC
franklin f
electron  e
planck_Charge planck

What is an Electric Charge?

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Protons repel protons whereas electrons are attracted to them. Similarly, electrons repel electrons but attract protons. The nature of the charge is closely related to the forces acting on it. The charge on an electron and a proton is of the same magnitude, i.e 1.6 x 10-19 C. However, a proton's charge is positive '+', while an electron's charge is negative '-'.

  • Electrons, like protons, are bound in an atom, however, not all of the electrons are tightly bound.
  • The electrons of an atom that are further away from the nucleus can be removed.
  • Due to a shortage in electrons, the number of protons exceeds the number of electrons when some electrons are removed from the atom.
  • The electrically neutral body hence becomes positively charged after the electrons are removed.
  • In the opposite situation, the body can obtain or gain electrons from an external source.
  • The number of electrons in the body increases in this situation, and the body becomes negatively charged.

Electric Charge

Electric Charge

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Electric Charge Formula

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The formula for electric charge is:

I.t = q

where,


Properties of Electric Charge

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The electric charge has a lot of different qualities. The following are some of the fundamental features of an electric charge:

  • In nature, electric charge is additive.
  • It is a preserved quantity.
  • It is possible to quantify electric charge.
  • A body attracts or repels another body due to the existence of an electric charge, depending on the type of the charge.
  • Friction between two distinct sorts of items causes one object to have a positive charge and the other to have a negative charge. 
  • Similar charges repel each other while positive and negative charges, for example, are attracted to one other.

Properties

Properties of Electric charge


Important Electrical Units

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Some of the important units used to measure electrical properties are:

Electrical Properties Unit Symbol
Capacitance Farad C
Charge Coulomb Q
Conductance Siemen G
Frequency Hertz Hz
Impedance Ohm Z
Inductance Henry H or L
Power Watts W
Voltage Volt V
Resistance Ohm R

Things to Remember

  • A property of matter that causes it to experience force is known as its electric charge.
  • According to Coulomb's Law- like charges repel while unlike charges attract each other.
  • Coulomb is a unit for measuring electric charge.
  • A particle's charge is essentially the sum of the charges of all the electrons in it.

Q = ne

  • where q = charge, 
  • n = number of electrons, 
  • and e = charge on 1 electron = 1.6 x 10-19C

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Previous Year Questions

  1. A current through a wire depends on time as… (BITSAT 2021)
  2. Find current, i… (KEAM 2018)
  3. The current (in ampere) drawn from a… (DUET 2009)
  4. A galvanometer has a resistance of… (DUET 2006)
  5. The current I in the circuit shown is… (MHT CET 2015)
  6. The potential difference that must be applied to stop the fastest… (NEET 2010)
  7. The potential difference (VA−VB)between the points… (NEET 2016)
  8. The potential differences across the resistance… (NEET 2016)
  9. A and B are two conductors carrying a current I in the same… (KCET 2002)
  10. The current passing through the ideal ammeter in the circuit… (KCET 2007)
  11. The potential difference between… (KCET 2008)
  12. The amount of charge flowing per second per unit area… (KEAM)
  13. Find the current in the 8W resistance in given circuit… 
  14. The potential difference between points… 
  15. Some electric bulbs are connected in series across a...(JKCET 2004)
  16. The mobility of free electrons… (JKCET 2010)
  17. The number density of free electrons in a copper conductor… (AMUEEE 2011)
  18. The potential difference applied to an X-ray tube… (JEE Advanced 2002)
  19. The mobility of charge carriers increases with...(DUET 2011)
  20. Identify the INCORRECT statement regarding a superconducting wire...

Sample Questions

Ques. What is the significance of an electric charge being a scalar quantity? (1 mark) 

Ans. The resulting current of two currents meeting at a junction is an algebraic sum, not a vector sum. A scalar quantity is thus an electric current.

Ques. What is the distribution of electric charges within the atom? (1 mark) 

Ans. Electric charges are carried by subatomic particles. In the nuclei of atoms, electrons have a negative charge while protons have a positive charge.

Ques. What is the difference between a positive and a negative charge? (2 mark) 

Ans. When an object loses electrons, the number of protons in the object exceeds the number of electrons in the object. As a result, the object gains a positive charge.

When an object gains electrons, it becomes negatively charged because the amount of electrons in the object exceeds the number of protons.

Ques. How are Charges made?  (3 mark) 

Ans. When we comb our hair with a plastic comb and then place little pieces of paper near the comb, the comb begins to attract the paper. When amber is rubbed with silk, it begins to attract pieces of paper as well. When a substance obtains a charge, it develops certain attractions and repulsions.

By rubbing one neutral object against another neutral object, an electric charge can be created. On the two separate items, two different sorts of charges form. A positive charge is created in one object, while a negative charge is created in the other.

Ques. What is the SI unit of electric charge? (1 mark) 

Ans. The SI unit used to measure electric charge is Coulomb.

Ques. What are the methods to supply electric charge to the object? (3 mark) 

Ans. Charging is the process of applying an electric charge to an object or removing an electric charge from an object.

There are three possible ways to charge an uncharged object:

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CBSE CLASS XII Related Questions

  • 1.
    The magnetic field in a plane electromagnetic wave travelling in glass (\( n = 1.5 \)) is given by \[ B_y = (2 \times 10^{-7} \text{ T}) \sin(\alpha x + 1.5 \times 10^{11} t) \] where \( x \) is in metres and \( t \) is in seconds. The value of \( \alpha \) is:

      • \( 0.5 \times 10^3 \, \text{m}^{-1} \)
      • \( 6.0 \times 10^2 \, \text{m}^{-1} \)
      • \( 7.5 \times 10^2 \, \text{m}^{-1} \)
      • \( 1.5 \times 10^3 \, \text{m}^{-1} \)

    • 2.
      The figure represents the variation of the electric potential \( V \) at a point in a region of space as a function of its position along the x-axis. A charged particle will experience the maximum force at:

        • P
        • Q
        • R
        • S

      • 3.
        Nuclides with the same number of neutrons are called:

          • Isobars
          • Isotones
          • Isotopes
          • Isomers

        • 4.
          Assertion : Photoelectric effect is a spontaneous phenomenon. Reason (R): According to the wave picture of radiation, an electron would take hours/days to absorb sufficient energy to overcome the work function and come out from a metal surface.

            • 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.

          • 5.
            In a Young's double-slit experiment, two waves each of intensity I superpose each other and produce an interference pattern. Prove that the resultant intensities at maxima and minima are 4I and zero respectively.


              • 6.
                Four long straight thin wires are held vertically at the corners A, B, C and D of a square of side \( a \), kept on a table and carry equal current \( I \). The wire at A carries current in upward direction whereas the current in the remaining wires flows in downward direction. The net magnetic field at the centre of the square will have the magnitude:

                  • \( \dfrac{\mu_0 I}{\pi a} \) and directed along OC
                  • \( \dfrac{\mu_0 I}{\pi a \sqrt{2}} \) and directed along OD
                  • \( \dfrac{\mu_0 I \sqrt{2}}{\pi a} \) and directed along OB
                  • \( \dfrac{2\mu_0 I}{\pi a} \) and directed along OA
                CBSE CLASS XII Previous Year Papers

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