Case Study Questions for Class 10 Science Chapter 13 Magnetic Effect of Electric Current
A student wants to study the working of electric motor. He used a model of DC motor for electromagnetism as shown in figure.
He fixed the two ends of the coil to a pair of curved elastic metal strips. The metal strips are connected to the power supply with a rheostat.
(i) The direction of rotation of the coil, when viewed from the front by the student is
(b) anti clockwise
(c) First half clockwise and other half anti-clockwise
(d) First half anti-clockwise and other half clockwise
(ii) The student is still testing on the feasibility of using metal strips in the model. His observations are given below.
I. As the current reverses in the coil for every half turn, the coil rotates in one direction.
II. The speed of rotation of the motor is increased, if the value of current is increased.
III. The direction of force, acting on the coil is given by Fleming’s left hand rule.
IV. The coil continues its rotation in magnetic field even if there is no current in circuit.
The correct observations made by him are
(a) I, II and IV (b) II, III and IV
(c) I, II and III (d) II and III
(iii) Commercial electric motors do not use
(a) an electromagnet to rotate the armature.
(b) effectively large number of turns of conducing wire in the current carrying coil
(c) a permanent magnet to rotate the armature
(d) a soft iron core on which the coil is wound
(iv) Which one of the following is true about electric motor?
(a) It converts electrical energy into mechanical energy
(b) It converts mechanical energy into electrical energy
(c) It converts magnetic energy into electric energy
(d) It converts electric energy into magnetic energy
(v) The direction of magnetic field at a place is coming out of the paper. A wire whose direction of current flow is as shown in the figure is placed there. In which direction is the force due to the magnetic field experienced by the wire?
(a) North-West direction
(b) North direction
(c) South-West direction
(d) South-East direction