A coil of insulated copper wire is connected to a galvanometer. What would
happen if a bar magnet is
(i) Pushed into the coil?
(ii) Withdrawn from inside the coil?
(iii) Held stationary inside the coil?
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Why is the earth pin thicker and longer than the live and the neutral pins?
An electron enters a magnetic field at right angles to it as shown in fig. The
direction of the force acting on the electron will be:
(a) to the right (b) to the left (c) out of the page (d) into the page
A current-carrying straight conductor is placed in the east-west direction. What
will be the direction of the force experienced by this conductor due to earth’s
magnetic field? How will this force get affected on? (a) reversing the direction of floe
of current (b) doubling the magnitude of current.
Draw the magnetic field lines representing uniform magnetic field.
Name any two devices which use permanent magnets.
Give two uses of electromagnets.
Where do we connect a fuse: with live wire or with neutral wire?
Give the factors that affect strength of magnetic field at a point due to a straight
conductor carrying current.
Can a 5 A fuse be used in wire carrying 15 A current? Why?
Why can’t two magnetic field lines ever intersect?
How can a solenoid be used to magnetise a steel bar.
How can it be shown that magnetic field exist around a wire carrying current?
A straight wire carrying electric current is moving out of plane of paper and is
perpendicular to it. What is the direction and type of induced magnetic field?
What kind of motor is used in: (i) A fan (ii) A battery operated toy
On what factor the strength of magnetic field of a solenoid depends?
How is Solenoid different from a circular coil?
What kind of quantity is magnetic field?
What is short circuiting in an electric circuit?
An Alternating Current has a frequency of 50 Hz. How many times it changes direction
in one second?
. On what effect of an electric current does a fuse work?
What is the frequency of AC (Alternating Current) in India?
On what effect of an electric current does an electromagnet work?
What will happen when -
a) Voltmeter is connected in series?
b) Ammeter is connected in parallel?
Why are fairy decorative lights always connected in parallel?
Why is the tungsten metal more coiled in the bulb and not installed in straight parallel wire
form?
What is the function of an earth wire? Why is it necessary to earth metallic appliances?
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When does an electric short circuit occur?
Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes?
State the rule to determine the direction of a (i) magnetic field produced around a straight conductor-carrying current, (ii) force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it, and (iii) current induced in a coil due to its rotation in a magnetic field.
Two circular coils A and B are placed closed to each other. If the current in the coil A is changed, will some current be induced in the coil B? Give reason.
A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is (i) pushed into the coil, (ii) withdrawn from inside the coil, (iii) held stationary inside the coil?
Name some devices in which electric motors are used?
Draw a labelled diagram of an electric motor. Explain its principle and working. What is the function of a split ring in an electric motor?
Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of magnetic field?
When is the force experienced by a current-carrying conductor placed in a magnetic field largest?
How does a solenoid behave like a magnet? Can you determine the north and south poles of a current-carrying solenoid with the help of a bar magnet? Explain.
List three sources of magnetic fields.
State whether the following statements are true or false.
(a) An electric motor converts mechanical energy into electrical energy.
(b) An electric generator works on the principle of electromagnetic induction.
(c) The field at the centre of a long circular coil carrying current will be parallel straight lines.
(d) A wire with a green insulation is usually the live wire of an electric supply.
At the time of short circuit, the current in the circuit
(a) reduces substantially
(b) does not change
(c) increases heavily
(d) vary continuously
The essential difference between an AC generator and a DC generator is that
(a) AC generator has an electromagnet while a DC generator has permanent magnet.
(b) DC generator will generate a higher voltage.
(c) AC generator will generate a higher voltage.
(d) AC generator has slip rings while the DC generator has a commutator.
The device used for producing electric current is called a
(a) generator
(b) galvanometer
(c) ammeter
(d) motor
The phenomenon of electromagnetic induction is
(a) the process of charging a body
(b) the process of generating magnetic field due to a current passing through a coil
(c) producing induced current in a coil due to relative motion between a magnet and the coil
(d) the process of rotating a coil of an electric motor
Which of the following correctly describes the magnetic field near a long straight wire?
(a) The field consists of straight lines perpendicular to the wire
(b) The field consists of straight lines parallel to the wire
(c) The field consists of radial lines originating from the wire
(d) The field consists of concentric circles centred on the wire
What precaution should be taken to avoid the overloading of domestic electric circuits?
An electric oven of 2 kW is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What result do you expect? Explain.
Name two safety measures commonly used in electric circuits and appliances.
Choose the correct option.
A rectangular coil of copper wires is rotated in a magnetic field. The direction of the induced current changes once in each
(a) two revolutions
(b) one revolution
(c) half revolution
(d) one-fourth revolution
Which sources produce alternating current?
Name some sources of direct current.
State the principle of an electric generator.
Explain different ways to induce current in a coil.
What is the role of the split ring in an electric motor?
What is the principle of an electric motor?
State Fleming's left-hand rule.
A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is
(a) towards south
(b) towards east
(c) downward
(d) upward
In Activity 13.7 (page: 230), how do we think the displacement of rod AB will be affected if (i) current in rod AB is increased: (ii) a stronger horse-shoe magnet is used: and (iii) length of the rod AB is increased?
Which of the following property of a proton can change while it moves freely in a magnetic field? (There may be more than one correct answer.)
(a) mass
(b) speed
(c) velocity
(d) momentum
The magnetic field inside a long straight solenoid-carrying current
(a) is zero
(b) decreases as we move towards its end
(c) increases as we move towards its end
(d) is the same at all points
The magnetic field in a given region is uniform. Draw a diagram to represent it.
Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.
Why don't two magnetic lines of force intersect each other?
List the properties of magnetic lines of force.
Draw magnetic field lines around a bar magnet.
Why does a compass needle get deflected when brought near a bar magnet?