According to Faraday's law a change in flux through a circuit produces an emf. Which of the following does not produce a change in flux?

(a) change in magnetic field
(b) change resistance
(c) change in area
(d) change in orientation angle

and your thinking is?

B is correct

To determine which of the given options does not produce a change in flux, let's first understand what flux is and how it is affected by each factor.

Flux is the measure of the total number of magnetic field lines passing through a given area. It depends on three factors: the strength of the magnetic field, the area through which the magnetic field lines pass, and the angle between the magnetic field lines and the area vector.

Now, let's consider each option:

(a) Change in magnetic field: If the strength of the magnetic field changes, it will result in a change in flux. This is because the number of magnetic field lines passing through the area will either increase or decrease, thereby changing the amount of flux.

(b) Change resistance: Resistance in a circuit does not directly affect the flux. Resistance refers to the opposition to the flow of electric current, and it doesn't modify the magnetic field strength, area, or their angles. Hence, changing resistance does not produce a change in flux.

(c) Change in area: If the area through which the magnetic field lines pass changes, it will result in a change in flux. Increasing or decreasing the area will affect the number of magnetic field lines passing through it.

(d) Change in orientation angle: The angle between the magnetic field lines and the area vector affects the flux. If the orientation angle changes, the effective area through which the magnetic field lines pass changes, leading to a change in flux.

Therefore, based on the above analysis, the correct answer is (b) change in resistance, as it does not produce a change in flux.