Assertion (A): When two identical loops of copper and Aluminium are rotated with same speed in the same magnetic field, the induced e.mn.f. will be same.
Reason (R), Resistance of the two loops are equal.

Options

A. Both A and R are true and R is the correct explanation of A
B. Both A and R are true but R is NOT the correct explanation of A
C. A is true but R is false
D. A is false and R is true

Explanation

To analyze the given assertion and reason, we can break down the problem step by step:

### Step 1: Understand the Assertion (A)
The assertion states that when two identical loops made of copper and aluminum are rotated with the same speed in the same magnetic field, the induced electromotive force (e.m.f.) will be the same.

### Step 2: Analyze the Induced e.m.f.
According to Faraday's law of electromagnetic induction, the induced e.m.f. (ε) in a loop is given by the formula:
\[ \epsilon = -\frac{d\Phi}{dt} \]
where \(\Phi\) is the magnetic flux through the loop. The magnetic flux is given by:
\[ \Phi = B \cdot A \cdot \cos(\theta) \]
where \(B\) is the magnetic field strength, \(A\) is the area of the loop, and \(\theta\) is the angle between the magnetic field and the normal to the surface of the loop.

### Step 3: Conditions for Induced e.m.f.
In this case, both loops are identical (same area \(A\)), rotated in the same magnetic field \(B\), and at the same speed. Therefore, the change in magnetic flux will be the same for both loops, leading to the conclusion that the induced e.m.f. will also be the same for both loops.

### Step 4: Understand the Reason (R)
The reason states that the resistance of the two loops is equal. However, the resistance of a loop depends on the material properties (resistivity), length, and cross-sectional area. Copper and aluminum have different resistivities, which means their resistances will not be equal, even if the loops are identical in dimensions.

### Step 5: Conclusion
- **Assertion (A)** is true: The induced e.m.f. will be the same for both loops.
- **Reason (R)** is false: The resistances of the two loops are not equal.

### Final Answer
- Assertion (A) is true.
- Reason (R) is false.