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# Magnetic fields around electric currents

Extracts from this document...

Introduction

921959.DOC        p./

 School: Class: Name: (      ) Subject: AL Practical Physics Date: Mark:

C16  Magnetic fields around electric currents I–straight wire (TAS)

Objective:

To use a search coil and CRO to investigate the magnetic field due to a straight wire carrying an a.c..

Theory:

In this experiment, a search coil is used to measure strength of magnetic field.For a long straight wire carrying current I ,there will be a magnetic field induced around the wire, given by.

Results and discussion

7        Why is this necessary to ensure the search coil is at the same level as the wire?

If

Middle

3.4

4.6

6.2

7.6

8

Current I/A

0.1

0.2

0.3

0.4

0.5

0.6

0.7

10        Plot a graph of l against I.

11        The length of the vertical trace is directly proportional to the magnetic field of the straight wire. How does the magnetic field vary with the current?

The greater the current, the greater is the magnetic field.

12        Tabulate the length l of vertical trace on CRO and distance r

Conclusion

respectively, the constant will found to be around 7.2 .Since different sets of the result are

more or less the same, they agree with the prediction by .

Source of error:

1. The search coil may not be the level of the wire.
2. There are some other electric wires in the room which can produce changing magnetic field.

Improvement:

1. Try to carry out the experiment in a room with fewer or no electric wires.
2. Move the search coil to ensure the maximum voltage is recorded.

Conclusion:

The magnetic field is directly proportional to current I and inversely proportional to distance r from the wire

Reference

Practical Physics for TAS (third edition), Oxford Press, 2005.

A-Level Practical Physics (Third Edition)© Oxford University Press 2005

This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.

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