Current Electricity

Assignment 2

Ohm's Law

Problems

1. The damage caused by a electric shock depend on the current through the body.

Can be felt 0.001 A

Painful 0.005 A

Loss of muscle control 0.015 A or more

Death (if exposed for more than 5-10 seconds) 0.070 A

The resistance of the human body changes if it is dry or wet.

Dry 100,000 ohms

Wet 5,000 ohms

1. What is the minimum voltage that would cause you to feel a shock when you have dry skin?
2. What would happen if this same voltage goes across a person with wet skin?
3. What is the minimum voltage that would cause pain to a person with wet skin?
4. In order for a person to be killed by electricity, how much voltage is needed for both dry skin and wet skin?

1. A light bulb draws 0.066 A when connected to a 6 V battery. If it is connected to a 9 V battery it will draw 0.075 A. Does the bulb obey Ohm's Law? (is the resistance the same in both cases?)

1. Devices that do not obey Ohm's Law usually change resistance with temperature.There is more resistance when the device is hotter.
   1. A toaster draws 0.4 A when it is heated up and plugged into a 120 V outlet. What is its resistance?
   2. If the resistance when it is first turned on is 1/5 of the hot resistance, how much current goes through it when it is initially turned on?