Question

1. OBSERVATIONAL EXPERIMENT: HOW TO INDUCE A CURRENT IN A COIL NOT CONNECTED TO A BATTERY The goal of this experiment is to observe 2 sets of videos to find a pattern for the conditions under which there is a current through a coil of wire that is not connected to a battery. Available equipment: Computer with internet connection a) First, make sure you know what a galvanometer is. A galvanometer is a device that registers electric current through it. It has a coil connected to an arrow with a spring, and a magnet (look at the photo below to identify these elements). When the current flows through the coil, the magnet exerts a torque on it and the coils starts turning pulling on the spring. The spring exerts an opposite torque on the coil. When these two torques are equal in magnitude, the coil stops rotating and the arrow attached to it shows a reading on the scale. The larger the current, the more force the magnet exerts on the coil, the greater the magnetic torque, the larger deflection of the arrow. As the current can flow in two directions, the scale of the galvanometer is set up with the zero in the middle, so that the needle can deflect to the right and to the left. Watch this video to see a galvanometer being calibrated. b) Watch this video of someone moving a magnet near a coil of wire connected to a galvanometer and this video of a coil of wire connected to a galvanometer moving near a permanent magnet. Record your observations i. ii. How many patterns can you identify in each video? List each of these patterns. iii. Are these patterns the same in both videos or there is a difference? c) Using the patterns in both experiments devise a preliminary rule that summarizes the condition(s) needed to induce a current in a coil. Write that rule in your report d) Examine the experiments listed in the table on the next page. Is the rule you devised consistent with the outcomes of these experiments? Explain.

Answer 1

1. when magnet is motionless , no current is induced in coil. the deflection of galvanometer is zero.

2. when a magnet is pushed quickly towards the coil , emf is induced in the coil and current flows int he circuit..therefore the galvanometer deflects towards right side .When we pull the magnet quickly the induced emf and current changes its direction and the galvanometer deflects towards left side,

3. when a magnet with its south pole is pushed quickly towards the coil the icurrent flows in the opposite direction to the current flowed when north pole is pushed towards it. When south pole is pulled away from it current changes it direction and deflection is towards right side,

4. In this case as magnet and coil planes are parallel no current flows in coil and galvanometer shows no deflection.

5. In this case first deflection is more and then deflection becomes zero as magnet becomes parallel to coil.

6. in this case also the galvanometer shows deflection towards left side and when south pole is placed it deflects towards right side by grasping and pulling flux changes so current floows in circuit.