Magnetic Field due to Straight Conductor
Magnetic Field Due To Current Through A Straight Conductor
The magnetic field lines around a current carrying straight conductor are concentric circles whose centre lies on the wire. To visualize the pattern of the magnetic field around a straight current—carrying conductor, we will do an experiment:
Take a stiff copper wire and pass it through the centre of a card board. Then, connect a battery source, a variable resistance through a switch i.e. K as shown in the figure
Place a compass on the cardboard and start the current by closing the switch. Compass needle get deflected and its deflection show the direction of magnetic field.
1. Mark the position of the north pole of the needle on the cardboard.
2. Place the compass ahead so that the south pole of the needle lies at the point marked for the previous position of the north pole.
3. Mark the new position of the north pole.
4. Repeat the step 2 and 3 till we reach the point from where you started.
5. Join all the points by a smooth curve to give a field line.
Similarly, draw other field lines at different distances from the wire. Draw arrows on the lines to show the direction of the magnetic field. If the current is weak, it will produce a weak magnetic field. Then the earth's magnetic field will have greater effect on the field lines, and they will not be circular.
From the experiment we observe that
1. If we increase the current through the conductor the magnetic field intensity is also increased. Hence the strength of the magnetic field produced by an electric current is directly proportional to the current.
where B is the magnetic field intensity, and I is the current Flowing through the conductor.
2. The more distant a point is from a current—carrying wire, the lesser is the intensity of the magnetic field at that point. So for a long straight current carrying wire, the strength of the magnetic field is inversely proportional to distance.
where B is the magnetic field intensity and d is the distance from the current carrying conductor.
3. If the direction of current is reversed, the field lines will still be circular, but the directions of the field lines will be reversed. This means, the north pole of the needle will point in the opposite direction.
We can sprinkle iron filings on the cardboard to see the arrangement of the field lines. The iron filings will get arranged in concentric circles, showing that the field lines due to a current passing through a straight wire are circular.
Which of the following are correct : (a) The more distant a point is from a current—carrying wire, the lesser is the intensity of the magnetic field at that point. (b) If we increase the current through the conductor the magnetic field intensity is decreased. | |||
| Right Option : A | |||
| View Explanation | |||
Which of the following are correct : (a) If we increase the current through the conductor the magnetic field intensity is increased. (b) The more distant a point is from a current—carrying wire, the more is the intensity of the magnetic field at that point. (c) If the direction of current is reversed, the field lines will still be circular, but the directions of the field lines will be reversed. | |||
| Right Option : C | |||
| View Explanation | |||
Nichrome is an alloy of: | |||
| Right Option : C | |||
| View Explanation |
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