ICSE-X-Physics
10: Electro Magnetism
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- #Section : AExercise 10 A
- Qstn #1Describe an experiment to demonstrate that there is a magnetic field around a current-carrying conductor.Ans : 1 Experiment:
In Fig, AB is a wire lying in the north-south direction and connected to a battery through a rheostat and a tapping key. A compass needle is placed just below the wire. It is observed that
(1) When the key is open i.e., no current passes through the wire, the needle shows no deflection and it points in the N-S direction (i.e. along the earth's magnetic field). In this position, the needle is parallel to the wire as shown in Fig.
(a).
(2) When the key is pressed, a current passes in the wire in the direction from A to B (i.e. From south to north) and the north pole(N) of the needle deflects towards the west [Fig.
(b)].
(3) When the direction of current in the wire is reversed by reversing the connections at the terminals of the battery, North Pole (N) of the needle deflects towards the east [Fig.
(c)].
(4) If the compass needle is placed just above the wire, the North Pole (N) deflects towards east when the direction of current in wire is from A to B [Fig.
(d)], but the needle deflects towards west as in fig
(e), if the direction of current in wire is from B to A.
The above observations of the experiment suggest that a current-carrying wire produces a magnetic field around it.
- Qstn #2Draw a diagram showing the directions of three magnetic field lines due to a straight wire carrying current. Also show the direction of current in the wire.Ans : 2
- Qstn #3How is the magnetic field due to a straight current-carrying wire affected if current in wire isAns : 3
- #3-adecreased,Ans : On decreasing the current the magnetic field lines become rarer.
- #3-breversed?Ans : The direction of magnetic field lines will get reversed.
- Qstn #4State a law, which determines the direction of magnetic field around a current-carrying wire.Ans : 4 Right hand thumb rule determines the direction of magnetic field around a current-carrying wire. It states that if we hold the current-carrying conductor in right hand such that the thumb points in the direction of flow of current, then the fingers encircle the wire in the direction of the magnetic fields lines.
- #5-aWhat will be the direction of magnetic field at a point just underneath it?Ans : The direction of magnetic field at a point just underneath is towards east.
- #5-bName the law used to arrive at the answer in part
(a).Ans : Right hand thumb rule.
- Qstn #6What will happen to a compass needle when the compass is placed below a wire and a current is made to flow through the wire? Give a reason to justify your answer.Ans : 6 A current carrying conductor produces a magnetic field around it and the magnetic needle in this magnetic field experience a torque due to which it deflects to align itself in the direction of magnetic field.
- Qstn #7Draw a labelled diagram showing the three magnetic field lines of a loop carrying current. Mark the direction of current and the direction of magnetic field by arrows in your diagram.Ans : 7
- Qstn #8A wire, bent into a circle, carries current in an anticlockwise direction. What polarity does this face of the coil exhibit?Ans : 8 Face of the coil exhibit North polarity.
- Qstn #9What is the direction of magnetic field at the centre of a coil carrying current in (i) clockwise, (ii) anticlockwise direction?Ans : 9
(i) Along the axis of coil inwards.
(ii) Along the axis of coil outwards.