2. Name the four advantages of storage cells in the order of their importance. Give your reasons for choosing this order.
3. Why are dry cells more suitable for operating a door-bell circuit, than a storage battery? Give two reasons.
4. The current for a city telephone system is provided by a storage battery. Why is this better than dry cells at each telephone?
5. An incandescent lamp takes 0.5 ampere at 110 volts. What power is required to operate it? How much energy will it transform in 1 minute?
6. How long would it take for this lamp to use a kilowatt hour of energy?
7. A street car used 100 amperes at 600 volts pressure. What power was delivered to it? Express also in kilowatts and horse-power.
8. An electric toaster takes 5 amperes at 110 volts. If it toasts a slice of bread in 2 minutes, what is the cost at 10 cents a kilowatt hour?
9. An electric flat iron takes 5 amperes at 110 volts. Find the cost of using it for 2 hours at 12 cents a kilowatt hour.
10. A 1/4 kilowatt motor is used to run a washing-machine for 5 hours. What is the expense for this power at 10 cents a kilowatt hour?
11. What is the efficiency of a motor that takes 7390 watts and develops 9 horse-power?