When a non magnetic metallic strip is moved away from between the poles of a horse-shoe magnet, there is

Options

A. Force acting on the strip to oppose the motion
B. Force acting on the strip to help the motion
C. No force acting on the strip
D. Couple acting on the strip so as to rotate it

Answer

To solve the problem step by step, we will analyze the situation of a non-magnetic metallic strip being moved away from the poles of a horseshoe magnet.

### Step 1: Understand the Setup
We have a horseshoe magnet with a North Pole and a South Pole. The magnetic field lines run from the North Pole to the South Pole. A non-magnetic metallic strip is placed between these poles.

**Hint:** Visualize the magnetic field lines and the position of the metallic strip relative to the magnet.

### Step 2: Movement of the Strip
When the non-magnetic metallic strip is moved away from the magnet, it is subjected to a changing magnetic environment. The magnetic field strength (B) in the area where the strip is located decreases as the strip is moved away.

**Hint:** Remember that moving the strip changes the magnetic flux through the area enclosed by the strip.

### Step 3: Change in Magnetic Flux
According to Faraday's law of electromagnetic induction, a change in magnetic flux (Φ) through a circuit induces an electromotive force (EMF). The magnetic flux is given by the product of the magnetic field (B) and the area (A) through which it passes.

**Hint:** Recall the formula for magnetic flux: Φ = B × A.

### Step 4: Induced EMF
As the strip is moved away, the change in magnetic flux induces an EMF in the strip. The induced EMF (ε) can be expressed as:
\[ ε = -\frac{dΦ}{dt} \]
This negative sign indicates the direction of the induced EMF according to Lenz's law.

**Hint:** Lenz's law states that the direction of induced current will be such that it opposes the change in magnetic flux.

### Step 5: Induced Current
The induced EMF causes a current to flow in the metallic strip. This current will create its own magnetic field. According to Lenz's law, this induced magnetic field will oppose the decrease in the magnetic field due to the movement of the strip.

**Hint:** Think about how the induced current behaves in response to the changing magnetic field.

### Step 6: Force on the Strip
The induced magnetic field from the current in the strip will exert a force that opposes the motion of the strip. Therefore, as the strip is moved away from the magnet, it experiences a force that acts in the direction opposite to its motion.

**Hint:** Consider Newton's third law and how forces interact in this scenario.

### Conclusion
When a non-magnetic metallic strip is moved away from between the poles of a horseshoe magnet, the force acting on the strip will oppose the motion. This is consistent with Lenz's law, which states that the induced current will act to oppose the change in magnetic flux.

**Final Answer:** The force acting on the strip will oppose the motion.