Question

MAGNETIC EFFECTS OF ELECTRIC CURRENT 1. Describe how you will locate a current carrying wire concealed in a wall? 2.Describe the construction and working of an electromagnet. Mention the factors on which its strength depends? 3.State qualitatively the effect of inserting an iron core into a current-carrying solenoid? 4.What is an electromagnet?How does it differ from a permanent magnet? 5.Name 2 alloys used for making permanent magnets?

Answer 1

(Q.) What will be the frequency of an alternating current, if its direction changes after every 0.05 s? 
(Ans) The time period (T) of one cycle would be = 2 x (0.05 s) = 0.1 s.
frequency, f = 1/T. Hence, f = (1 / 0.1) = 10 Hz.
(Q.) What is the principle on which working of electric generator is based? What are its important parts? 
(Ans) The working of electric generator is based on the principle of electromagnetic induction.
Important parts of electric generator are armature, slip rings, brushes and field magnets.
(Q.) Why two magnetic lines of force don’t intersect each other?  
(Ans) If so then at the point of intersection there will be two different directions of magnetic field which is not possible.
(Q.) Give two methods by which we can increase the strength of magnetic field produced by a circular coil carrying current? 
(Ans) The two methods by which we can increase the strength of magnetic field are given below:-
1. By increasing the number of turns of wire in the coil.
2. By increasing the current flowing through the coil.
(Q.) What are the patterns of magnetic field lines inside and outside of a solenoid? What do they indicate? (Ans) (i)The field lines inside the solenoid are parallel straight lines. This indicates that the magnetic field is uniform and is therefore, same at all points inside it.
(ii)The field lines outside the solenoid are curved lines. This indicates that the magnetic field is non-uniform.
(Q.) What are the factors which govern the force experienced by a current carrying conductor placed in a uniform magnetic field depends? 
(Ans) The factors which govern the force expericed by conductor which is placed in a uniform magnetic field are:-
1. strength of the magnetic field in which conductor is placed.
2. strength of current flowing through the conductor.
3. length of conductor.

(Q.) Distinguish between an electric motor and generator? 
(Ans) The major differences between an electric motor and generator are stated below:
Electric Motor                                                                                            Generator 
1. It converts electrical energy into mechanical energy. 
2. It needs electrical energy for its working. 3. They are used as water pumps, marble grinders e.t.c
Generator 1. It converts mechanical energy into electrical energy 
2. It needs mechanical energy for its working. 
3. They are used as water pumps, marble grinders e.t.c 3. Diesel generator, hydro-electric generator are the examples of it.