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Found in: Page 809

### College Physics (Urone)

Book edition 1st Edition
Author(s) Paul Peter Urone
Pages 1272 pages
ISBN 9781938168000

# Draw a diagram and use RHR-1 to show that the forces on the top and bottom segments of the motor’s current loop in Figure 22.34 are vertical and produce no torque about the axis of rotation.

Forces on the top and bottom segments are of equal magnitude and in opposite directions. Hence produce no torque about the axis of rotation.

See the step by step solution

## Step 1: Right-Hand Rule-1

The right-hand rule states-1 (RHR-1) that the direction of the magnetic force on a moving charge is perpendicular to the plane formed by v and B.

## Step 2: Defining torque

Torque is defined as${}^{\mathfrak{r}=\mathrm{r}\mathbf{Fsin}\mathrm{\theta }}$; where r is the distance, F is the applied force, and${}^{\mathrm{\theta }}$ is the angle between r and F.

## Step 3: Defining forces on the top and bottom segments

1. According to RHR-1, the thumb is in direction of the velocity, and the fingers point in the direction of B.

2. That means for the top segment, the direction of velocity is from left to right, and force points in the direction perpendicular to the palm and upwards.

3. For the bottom segment, the direction of velocity is from right to left and force is perpendicular to the palm but pointing downwards.

4. Finally, the forces acting on the top and bottom segments are of equal magnitude but the direction is opposite, with one pointing vertically up and the other vertically down.

5. Therefore, these two forces produce no torque about the axis of rotation.

## Step 4: Diagram for top and bottom segments

Let us draw the required segments,