Electric Current

Electric current

1. Calculate the average electric current in a wire when a charge of 150 C passes in 30s? I = Q/t = 150/30 = 5A
2. The current in a small torch bulb is 0.20 A. What total electric charge which passes through a point circuit in 12 minutes? 1.4 x10²How many electrons pass through this point in this time? 1.4 x10² /1.8 x 10^-19 = 9 x 10²⁰
3. In the circuit opposite the three bulbs are identical and reach hill brightness when the current is 0.20A. Bulb B is observed to be at full brightness. Which (if any) of the other bulbs will be at full brightness, and what is the current in each of them? B,C

B = 0.2A, C = 0.2A, D = 0.05A

4. A new electric cell was joined in series with a bulb and an ammeter. The initial current was 0.30 A. At subsequent intervals of 1 hour the readings on the ammeter were: 0.27A, 0.27A, 0.26A, 0.25 A, 0.23A, 0. 19A, 0.09A, 0.03 A, and at 9 hours the ammeter reading had become negligibly small.
   (a) Plot a graph of current against time.
   (b) What does the area under the graph represent? Total charge
   (c) How much electric charge passes through the circuit when a current of 0.10 A passes for 1 hour? 360C
   (d) What is the total electric charge which passes through the cell in the 9 hours? 6.3kC
5. In a gas discharge tube containing hydrogen the current is carried partly by (positive) hydrogen ions and partly by electrons. An ammeter in series with the tube indicates a current of 1.5 mA. If the rate of passage of electrons past a particular point in the tube is 6.0 x 10¹⁵ s^-1, find the number of hydrogen ions passing the same point per second. 3.4 x10¹⁵ s^-1