RP 11: Investigate, using a search coil and oscilloscope, the effect on magnetic flux linkage of varying the angle between a search coil and magnetic field direction.

What is the method used to investigate how the emf induced in a search coil depends on the angle between it and the magnetic field? (7)

- Mount a large circular coil vertically using a stand, and place a protractor card beneath it.

- Attach a search coil to another stand so that its plane is initially parallel to the plane of the large circular coil.

- Connect the circular coil to a 50 Hz AC power supply, and connect the search coil to an oscilloscope.

- Switch on the AC supply and adjust the voltage and time base settings on the oscilloscope.

- Read and record the peak-to-peak voltage shown on the oscilloscope.

- Rotate the search coil so that the angle (θ) between its plane and the plane of the circular coil increases by 10° increments, up to 90°.

- For each angle, record the induced emf and repeat each measurement twice to calculate a mean value.

What equipment is required to investigate how the induced emf varies with angle in a coil system? (6)

- Oscilloscope.

- Large circular coil.

- Stands.

- 50 Hz AC supply.

- Protractor card.

- Search coil.

What does a setup used to investigate how the emf induced in a search coil depends on the angle between it and the magnetic field look like? (3)

What is the independent variable in the induced emf and angle experiment? (1)

The independent variable is the angle (θ) between the search coil and the magnetic field.

What is the dependent variable in the induced emf and angle experiment? (1)

The dependent variable is the peak emf induced in the search coil.

What are the controlled variables in the induced emf and angle experiment? (4)

- The controlled variables include the number of turns in the search coil.

- Another controlled variable is the magnetic field strength.

- Another is the frequency of the AC supply.

- The final controlled variable is the distance between the coils.

What should be calculated to investigate the relationship between emf and angle? (1)

For each measurement, calculate cos(θ) and put this in a table alongside the mean emf.

What graph is plotted to determine the relationship between emf and angle? (1)

Plot a graph of induced emf against cos(θ).

What does a straight-line emf against cos(θ) graph indicate? (1)

If the graph is a straight line through the origin, it confirms that emf is proportional to cos(θ), consistent with the equation ε = BANωcos(θ).

What is one safety precaution in the induced emf and angle experiment? (1)

Standard care should be taken with electrical equipment.

How can angle measurement uncertainty be reduced in this experiment? (1)

Use a set square, or align your eye carefully with the protractor from far away, to reduce parallax error in reading the angle.