Q. The strength of magnetic field inside a long current carrying straight solenoid is:
Inside the solenoid magnetic field lines are straight. This indicates strong magnetic field. Hence, magnetic field is uniform at all points inside the solenoid.
Q. The direction of force acting on a current carrying conductor placed in a magnetic field can be obtained by:
(a) Fleming’s left hand rule.
(b) Fleming’s right hand rule.
(c) Clock face rule.
(d) Ampere’s swimming rule.
Ans. (a) Fleming’s left hand rule.
The direction of force acting on a current carrying conductor placed in a magnetic field can be obtained by Fleming’s left hand rule. According to this rule, when a current-carrying conductor is placed in an external magnetic field, the conductor experiences a force perpendicular to both the field and to the direction of the current flow.
Q. The device used for producing electric current is called a :
Ans. (a) Generator
A.C. generator is used to convert mechanical energy to electrical energy.
Q. The essential difference between an A.C. generator and a D.C. generator is that:
(a) A.C. generator has an electromagnet while a D.C. generator has permanent magnet.
(b) D.C. generator will generate a higher voltage.
(c) A.C. generator will generate a higher voltage.
(d) A.C. generator has slip rings while the D.C. generator has a commutator.
Ans. (d) A.C. generator has slip rings while the D.C. generator has a commutator.
Most essential difference between A.C. generator and D.C. generator is using slip ring in A.C. generator and commutator in D.C. generator.
Q. At the time of short circuit, the current in the circuit:
Ans. (c) Increases heavily
A short circuit occurs when circuit current rises rapidly and the electric circuit drown an heavy amount of current from the supply.
Q. State Fleming's Left Hand Rule.
Ans. According to this rule, stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular to each other. If the first finger points in the direction of magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor.
Q. What is the principle of an electric motor?
Ans. Electric motor works on the principle that ‘when a rectangular coil is placed in a magnetic field and current is passed through it, a force acts on the coil which rotates it continuously. Thus, when the coil rotates, the shaft attached to it also rotates converting the electrical energy supplied to the motor to the mechanical energy of rotation.
Q. What is the role of a split ring in an electric motor?
Q. Why does a compass needle get deflected when brought near a bar magnet?
Ans. When a compass needle is brought near a bar magnet, the compass needle experiences a deflection due to the interaction of magnetic fields of the compass needle and the bar magnet.
Q. When does an electric short circuit occur?
Ans. When live and neutral wires touch each other, the resistance suddenly decreases and current increases. This leads to excessive heating of wire which manifests in the form of sparks. This is called short circuit.
Q. What is the function of an earth wire? Why is it necessary to earth metallic appliances?
Q. Answer the following questions:
(i) Name and state the rule to determine the polarity of the two faces of a current carrying circular loop.
(ii) State Fleming’s Left Hand Rule.
Q. Answer the following questions:
(i) What is the principle of an electric motor?
(ii) What is the role of a split ring in an electric motor?
(iii) Define magnetism.
Q. Two coils A and B are placed close to each other. If the current in coil A is changed, will some current be induced in the coil B ? Given reason.
Q. When is the force experienced by a current-carrying conductor placed in a magnetic field largest?
Q. Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clock-wise. Apply the right hand rule to find out the direction of the magnetic field inside and outside the loop.
Q. A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is:
Q. Name some devices in which electric motors are used.
Q. Explain different ways to induce current in a coil.