# Magnetic Field

1. May 7, 2006

### frozen7

iv)The magnetic field, B at the center of a circular current loop of radius r carrying current I, is given by the expression . If one of the long straight wires is bent 90o in a circular arc of radius r (refer to Figure B1). What is the magnetic field at the center of the arc P?

Can anyone help me? Help needed.

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2. May 7, 2006

### Päällikkö

Use the Biot-Savart law.

3. May 9, 2006

### frozen7

What i know is for the arc section, the magnetic field should be (miu)I / 2r and for the straight wire is (miu)I / 2(pie)r. I dont know how to start this question. Should I just sum up both magnetic field?

4. May 9, 2006

### Päällikkö

Using the superposition principle, yes you may add them together. The $$\frac{\mu I}{2r}$$ seems to be the magnetic field generated by a whole circle. Thus the field generated by the arc in the picture is $$\frac{1}{4}\frac{\mu I}{2r}$$.

EDIT: Replied the same minute .