CBSE Class 10 Science 2019 · Paper 31/3/1 · Question 21

(a) Fleming's left-hand rule: stretch the thumb, forefinger and middle finger of the left hand so that they are mutually perpendicular. If the forefinger points in the direction of the magnetic field and the middle finger in the direction of the current, then the thumb points in the direction of the force on the conductor (the direction of its motion). (b) Electric motor - the labelled diagram is the figure 'A simple electric motor (labelled)'. It shows a rectangular coil ABCD of insulated copper wire (the armature) between the poles N and S of a magnet, with arms AB and CD perpendicular to the field; the two ends of the coil joined to the halves P and Q of a split ring (commutator) on the axle; carbon brushes X and Y pressing on P and Q; and a battery and key K joined to the brushes. Labels: N, S, coil ABCD, axle, split ring P and Q, brushes X and Y, battery, key K.