20.2c Ex1 MJ13 P42 Q5 Parallel Wires Forces | A2 Magnetic Fields | CAIE A Level 9702 Physics

Example 1 - 9702/42/M/J/13: (a) Define the tesla. (b) Two long straight vertical wires X and Y are separated by a distance of 4.5 cm, as illustrated in Fig. 5.1. The wires pass through a horizontal card PQRS. The current in wire X is 6.3 A in the upward direction. Initially, there is no current in wire Y.
(i) On Fig. 5.1, sketch, in the plane PQRS, the magnetic flux pattern due to the current
in wire X. Show at least four flux lines.
(ii) The magnetic flux density B at a distance x from a long straight current-carrying wire is given by the expression B = μ0I/2πx where I is the current in the wire and μ0 is the permeability of free space. Calculate the magnetic flux density at wire Y due to the current in wire X.
(iii) A current of 9.3 A is now switched on in wire Y. Use your answer in (ii) to calculate
the force per unit length on wire Y.
(c) The currents in the two wires in (b)(iii) are not equal. Explain whether the force per unit length on the two wires will be the same, or different.
#9702s13p42 #A2parallelWiresP4 #Lv2
Error note for equation:
If we define F_A as force by A on B, then
B = field created by A = (μ)(I_A)/(2πx)
I = current of B
If we define F_A as force on A by B, then
B = field created by B = (μ)(I_B)/(2πx)
I = current of A
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[@m.imrannawaz5634]

🎉🎉🎉🎉🎉🎉

[@pradiptaroy6755]

How do we know that the force depends on the product of both wires current at 13:05?

[@ETphysics]

One of the earlier videos discussed that magnetic field due to a wire, B is proportional to its current. E.g. equation B = μI/2πx From Fleming's left hand rule, the force on conductor F = BIL. So if we sub B into the force equation, we get force that is proportional to the product of both currents!

[@gristlevonraben]

very interesting