Wheel is spun clockwise in magnetic field

[Masafi]

A wheel is spun clockwise in a vertical plane at a constant rate. At the place where the experiment is performed, the Earth’s magnetic field is in a horizontal direction. It acts into and perpendicular to the paper.

The rim is the outside of the wheel, and the hub is the centre.

A constant e.m.f. is induced across the length of each spoke.

Label the hub and rim either plus or minus to show the polarity of the e.m.f.

Using Flemings Right Hand rule, thumb points to centre, index finger into page, so induced emf is clockwise. How do I use this to determine whether the rim is positive or negative, and then for the hub?

 

[jbsteele]

The rim is positive and the hub is negative. Fleming's right hand rule states that the direction of the induced emf is in the same direction as the thumb when the index finger points into the page and the thumb points to the centre. This indicates that the induced emf is clockwise, meaning that the rim is positive and the hub is negative.

 

[kerimek]

Based on the given information, it can be determined that the rim of the wheel is positive and the hub is negative. This is because the induced e.m.f. is clockwise, which means the current flows in a direction from the hub towards the rim. According to Flemings Right Hand rule, the thumb points towards the centre (hub) and the index finger points into the page, indicating that the current flows from the hub towards the rim. This means that the rim must be positive and the hub must be negative.

To further clarify, when a wheel is spun clockwise in a magnetic field, the motion of the wheel creates a changing magnetic flux, which in turn induces an e.m.f. in the wheel. This e.m.f. causes a current to flow in the spokes of the wheel, with the direction of the current being from the hub towards the rim. Since current flows from positive to negative, the rim must be positive and the hub must be negative.

In conclusion, based on Flemings Right Hand rule and the direction of the induced e.m.f., it can be determined that the rim of the wheel is positive and the hub is negative. This is because the current flows from the hub towards the rim in a clockwise direction, as the wheel is spun in a clockwise direction.