Assertion If a straight wire is moved in a magnetic field, no emf will be induced across its two ends as the circuit is not closed.
Reason Since, the circuit is not closed, induced current will be zero.

Options

A. If both Assertion and Reason are corrent and Reason is the corrent explanation of Assertion.
B. If both Assertion and Reason are correct but Reason is not the correct explanation of Assertion.
C. If Assertion is true but Reason is false.
D. If Assertion is false but Reason is ture.

Explanation

To solve the question regarding the assertion and reason, let's break it down step by step:

### Step 1: Understand the Assertion
The assertion states that if a straight wire is moved in a magnetic field, no EMF will be induced across its ends because the circuit is not closed.

### Step 2: Analyze the Situation
According to Faraday's law of electromagnetic induction, an electromotive force (EMF) is induced in a conductor when it experiences a change in magnetic flux. The formula for the induced EMF (ε) in a straight wire of length L moving with velocity v in a magnetic field B is given by:
\[ \text{EMF} = B \cdot L \cdot v \]

### Step 3: Determine the Validity of the Assertion
Even if the circuit is not closed, the movement of the wire in the magnetic field still induces an EMF across its ends. Therefore, the assertion that no EMF will be induced is incorrect.

### Step 4: Understand the Reason
The reason states that since the circuit is not closed, the induced current will be zero. This is true because for current to flow, there must be a closed path. If the circuit is open, the induced current cannot flow, even though an EMF is present.

### Step 5: Conclusion
Based on the analysis:
- The assertion is false because EMF can still be induced even if the circuit is not closed.
- The reason is true because the induced current will indeed be zero if the circuit is open.

Thus, the correct conclusion is that the assertion is false and the reason is true.

### Final Answer
The assertion is false, and the reason is true. Therefore, the correct option is option 4.

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