## 7 Common Problems in Magnetic Field

- Category: High School
- Written by fisikastudycenter

physics.fisikastudyceter.com-Discussing 7 common questions in magnetic field, finding the magnetic field around wire or conductor with current in it.

1) A long and straight conductor with current of i = 2 A is shown in the below figure:

Find :

a) magnetic field at point P

b) direction of the magnetic field at P

c) magnetic field at point Q

d) direction of the magnetic field at Q

**Disscussion**

a) magnetic field (B) at distance a from along, stright conductor carrying current I :

So then the magnetic field at point P :

b) Using the right hand rules to determine the direction of magnetc field,

4 finger express the magnetic field direction (the conductor position is in hand holding)

thumb expresses current direction

Then we get the direction of magnetic field is out toward the reader.

c) The magnetic field at point Q :

d) the magnetic field direction is into reading sheet

2) Given a figure below

Find the magnitude of magnetic field at point P!

**Discussion**

The magnetic field produced by I_{A} is in opposite direction with the magnetic field that is produced by I_{B}, find the magnetic fields and then get the sum:

The resultant direction is in the same direction with the magnetic field that is produced by I_{B}, that is into our reading sheet.

3) Two conductors A and B that are 1 m away, with currents in the conductors respectively 1 A and 2 A as the figure below!

Find the location of point C where the magnetic field magnitude is 0 Tesla!

**Solution**

To get zero magnetic field resultant at point C, the magnetic field produced by A must be in the same magnitude as B, but in the opposite direction each other. Assume the distance is x that is from from conductor A, so then

4) Three conductors with the currents in them and the directions as the figure below

Find the magnitude of magnetic field at point P that is 1 m away from the third conductor!

**Solution**

We have three vectors of magnetic field that are produced by the conductors. Find the magnitude of each, and then get the resultant

The direction is into our reading sheet

5) The conductor A with I_{1} in it and the conductor B with I_{2} respectively 2 A dan 3 A. Both currents are in the same direction that is out toward the reader.

Find the magnetic field at point C that is form an equilateral triangle with point A and B!

**Solution**

Finding B1 dan B2

Use vector formula and keep 10^{−7} as x to simplify the calculation.

The direction of magnetic field :

6) Given circular conductor and a long-straight conductor as the figure below. Find the magnetic field at point P!

**Solution**

The magnetic field produced by circular conductor (a half) with its direction into reading sheet, B_{1} and the magnetic field produced by a long-straight conductor, with its direction is out toward the reader, B_{2} :

The final resultant direction is the same direction with B_{1} direction.

7) Find the magnetic field at point P, that is at distance of 8 cm and the current in the conductor is 1 A!

**Solution**