Download Worksheet 1 - Magnetic Effects of Electric Current

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Magnetic effects of electric current
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worksheet-1
A motors convert’s _________ energy into __________ energy.
SI units of magnetic field strength is __________
No force acts on a current carrying conductor when it is _________ to the magnetic field.
The bar magnet is a __________ magnet
An electromagnet is a__________ magnet.
An electromagnet works on the magnetic effect of _________
Larger the number of turns in the solenoid, greater will be the __________ produced.
A current flowing in a wire always gives rise to a _______round it.
Law of induction were given by________.
_________ Law gives the direction of induced current.
True or false
1. The magnetic lines of force produced by a straight current carrying conductor are straight in nature.
2. Slip rings are used in an AC generator.
3. The strength of an electromagnet increases or decreases the amount of current flowing through it.
4. The thinner the fuse wire, the greater its capacity
5. The SI unit of electrical potential is the coulomb
6. A commutator is used in a DC dynamo.
7. The device used for producing electric current is called generator
8. A wire with green insulation is usually the live wire.
9. The frequency of DC is zero.
10. Electrical fuse is a safety device.
Multiple choice questions
1. It is a common notion that the earth’s magnetism is due to the
(a) Presence of a huge permanent magnet in the interior of the earth.
(b) Presence of the electric current circulation in the interior of earth.
(c) Influence of the sun’s magnetic field
(d) Influence of a nuclear explosion.
2. The force between two parallel wires carrying current has been used to define.
(a) Ampere
(b) coulomb
(c) Volt
(d) watt
3. A magnetic field cannot expert any force on a
(a) Moving magnet
(b) moving charges
(c) Stationary magnet
(d) stationary charge
4. The force of repulsion between two parallel wires is ࢌ when each one of them carries a certain current ࡵ. If
the current in each is doubled, the force between them would be
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(a) ૛ࢌ/ૡ
(b) ૛ࢌ
(c) ૝ࢌ
(d) ࢌ
An electric iron draws a current of 4 A when connected to a 220V main. Its resistance must be
(a) 1000Ω
(b) 55Ω
(c) 44Ω
(d) none of these
The resistance of a conductor is reduced to half its initial value. In doing so the heating effects in the
conductor will become.
(a) Half
(b) double
(c) One-fourth
(d) four times
The coil of a heater is cut into two equal halves and only one of them is used in the heater. The ratio of the
heat produced by this produced by this half of coil to that produced by the original coil is
(a) 2:1
(b) 4:1
(c) 1:2
(d) 1:4
The fact that current associated with a magnetic field was discovered by
(a) Oersted
(b) Maxwell
(c) Faraday
(d) Ohm
Ampere rule is used to find the
(a) Direction of current.
(b) Direction of magnetic field.
(c) Direction of motion of conductor.
(d) Magnitude of current.
A magnetic field can exert force on a
(a) Stationary magnet
(b) Moving charge
(c) Moving magnet
(d) All the above
A compass needle just above a wire in which electrons are moving to the east, will point
(a) East
(b) west
(c) North
(d) south
Choose the correct statement
(a) Lines of force are not imaginary lines.
(b) Lines of force cannot be mapped on paper on paper.
(c) Lines of force do not intersect each other.
(d) Lines of force always intersect each other.
A motor converts
(a) Mechanical energy into electrical energy.
(b) Mechanical energy into sound energy.
(c) Electrical energy into mechanical energy.
(d) Electric energy into sound energy.
A dynamo
(a) Mechanical energy into sound energy.
(b) Mechanical energy into electrical energy.
(c) Electrical energy into mechanical energy.
(d) Electric energy into sound energy.
By inserting a soft iron piece into a solenoid the strength of the magnetic field
(a) Increases
(b) Decreases
(c) First decrease then increase.
(d) Remains unchanged.
By increasing the number of turns in the coil, the strength of the magnetic field
(a) Decreasing
(b) Increasing
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(c) First decreases then increases
(d) Remains unchanged
If the current in core decreases, the strength of magnetic field
(a) Decreases
(b) Increases
(c) Sometimes decreases and sometimes increases
(d) Remains unchanged
The unit of magnetic flux is
(a) Weber
(b) Gauss
(c) Tesla
(d) Weber/࢓૛
Fleming’s right hand rule gives
(a) The magnitude of the induced emf.
(b) The magnitude of the magnetic field
(c) The direction of induced emf
(d) Both magnitude and direction of the induced emf.
The unit of induced emf is
(a) Ampere
(b) Joule
(c) Volt
(d) Electron volt.
The phenomenon of electromagnet induction was discovered by
For making electromagnet the best material.
The intensity of a magnetic field is defined as the force experienced by a
For current flowing from north to south, the compass placed above the wire, would deflect in the following
direction
There will be no force between two currents if that are
A long current carrying wire PQ is free to move when placed in a magnetic field B at right angles to the wire,
as shown in Fig.7.31 (the )