What is the magnetic effect of electric current?

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Jasmine Grover

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When an electric current is passed through a wire, it starts acting like a magnet. This is known as the magnetic effect of the electric current. When the current is stopped, the wire loses its magnetic effect. 

  • A magnetic field is generated as a result of the magnetic effects of electric currents. 
  • At any given point, the magnetic field is a vector field as it is specified by direction as well as magnitude.
  • Electric motors are a popular application of the magnetic effects of electric current.
  • A current carrying conductor gives rise to a magnetic field through magnetic lines of force or magnetic field lines.
  • Around a straight conductor, the magnetic field lines are concentric. 

Magnetic effect of the electric current

Fleming’s Right Hand Rule

Fleming’s Right Hand Rule states that if our right hand thumb, forefinger and middle finger are arranged perpendicular to each other, then – 

  • The thumb points the direction of the magnetic force.
  • The forefinger points the direction of the magnetic field.
  • The middle finger represents the direction of the current.

Fleming’s Left Hand Rule

Fleming’s Left Hand Rule states that if our left hand thumb, forefinger and middle finger are perpendicular to each other, then – 

  • The thumb denotes the magnetic force direction.
  • The forefinger denotes the magnetic field direction.
  • The middle finger denotes the direction of the current.

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CBSE CLASS XII Related Questions

  • 1.
    Two heaters rated as \((P_1,V)\) and \((P_2,V)\) are connected in series across a dc source of \(V/2\) volt. The power consumed by the combination will be –

      • \((P_1+P_2)\)
      • \(\dfrac{P_1+P_2}{2}\)
      • \(\dfrac{P_1P_2}{2(P_1+P_2)}\)
      • \(\dfrac{P_1P_2}{4(P_1+P_2)}\)

    • 2.
      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 \( F \)

      • 3.
        Four independent waves are expressed as \[ (i)\; y_1=A_1\sin\omega t, \] \[ (ii)\; y_2=A_2\sin 2\omega t, \] \[ (iii)\; y_3=A_3\cos\omega t, \] \[ (iv)\; y_4=A_4\sin\left(\omega t+\frac{\pi}{3}\right) \] The interference between two of these waves is possible in

          • (i) and (iii) only
          • (iii) and (iv) only
          • (i), (iii) and (iv) only
          • All of them

        • 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.
              The figure shows three point charges kept at the vertices of triangle ABC. The net electric field, due to this system of charges, at the midpoint M of base BC will be:

                • \( \frac{q}{4 \pi \epsilon_0 l^2} \) pointing along MA
                • \( \frac{q}{\pi \epsilon_0 l^2} \) pointing along AM
                • \( \frac{q}{2 \pi \epsilon_0 l^2} \) pointing along AM
                • Zero

              • 6.
                Photoemission of electrons occurs from a metal (\( \phi_0 = 1.96 \, \text{eV} \)) when light of frequency \( 6.4 \times 10^{14} \, \text{Hz} \) is incident on it. Calculate: Energy of a photon in the incident light, The maximum kinetic energy of the emitted electrons, and The stopping potential.

                  CBSE CLASS XII Previous Year Papers

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