Class XII CBSE , Physics

1. Kendriya Vidyalaya
Karwar
Physics Project
Class XII A
By: Atit Gaonkar

2. Force Due To Parallel
Current Carrying
Conductor

10. TOPIC
• Force Due To Parallel
Current Carrying
Conductor

11. Force Due To Magnetic
Field is placed in an
• When a current-carrying conductor
external magnetic field B, the magnetic force on the
conductor is given by:
• F = I (L x B)
• F = I L B sin θ

12. Let L1 & L2 be two current carrying conductors,
carrying current I1 & I2 separated by a
distance ‘a’ producing magnetic field B1 & B2
respectively

13. • Consider two parallel wires of equal length carrying
a steady current:
The two wires will exert magnetic forces on each
other.
Wire 1 will exert a magnetic force on wire 2, wire 2
will exert a magnetic force on wire 1.
• From Amperean Law we know that the magnetic
fields B1 & B2 :
• B1 = (μ * I1)/ 2Πa
• B2 = (μ * I2)/ 2Πa

15. • The wires are separated by distance ‘a’ and carry
currents I1 and I2 in the same direction.
• Wire 2, carrying current I2, sets up a magnetic field
B2 at the position of wire 1.
• The direction of the magnetic field B2 is known by
using Right Hand Thumb Rule and the direction is
perpendicular to the wire

16. • Therefore F21 = I1 (L x B2)
• As Angle Between L And B2 is 90
• So F21 = I1 L B2
• Therefore the force F21 = I1 L (μ I2) / 2Πa

17. • Rewriting the force per unit length :
• F/L = I1 (μ I2)/ 2Πa
• So, let F/L = F’
•
F’ = I1 (μ I2) / 2Πa
•
F’ = (μ I1 I2 ) / 2Πa
• The direction of F1 is towards the other conductor
and is determined by using the right hand rule
(fingers of right hand in direction of current I; palm
facing in the direction of B; thumb points in the
direction of Force)

18. • As the new force is directly proportional to I1 & I2 so
the new force of wire1 and wire2 over each other
will be same.
• The magnetic force that wire 1 exerts on wire 2
(F1 on 2) is equal in magnitude to and opposite in
direction to F1 (F2 on 1).
• Wire 1 and wire 2 will attract each other.

19. • Note: Parallel conductors carrying currents in the
same direction attract each other & parallel
conductors carrying currents in opposite directions
repel each other.

20. • So,
 Parallel wires with current flowing in the same
direction, attract each other.
 Parallel wires with current flowing in the opposite
direction, repel each other.

21. • Therefore
• Vector F21 = - Vector F12
• But | F21 | = | F12 |
• Therefore F’ = (μ I1 I2 ) / 2Πa
• When I1 = I2 = I Ampere , a = 1m , then
F’ = 2 * 10-7 N/m

22. • So,
• 1 Ampere can be defined as “When two current
carrying conductors placed at a separation of 1m,
and if they experiences a force of 2 * 10-7 N/m, then
the current through the conductors are said to be
1 Ampere.