1. Describe the methods by which an electric potential develops in primary cells and dry cells.

2. Describe the methods by which an electric potential develops in generators and

thermocouples.

3. Identify the scenarios below as to whether they would increase or decrease the resistance of

an electric current through a body.

a. Increase the length of the conductor

b. Utilize a conductor with a larger cross-section

C. Cool the conductor to lower its temperature

4. If 0.8 Wh of electrical energy is lost as heat, how much heat energy (in Btu) is produced?

5. How many kilowatt-hours of energy would be used by a 40 W bulb that runs for 10 hours

every day during the course of one year?

In primary cells, an electric potential develops through chemical action between the plates within the cell. Positively charged ions of zinc enter the acid and free electrons released from zinc atoms collect on the zinc plate, which results in a negative charge. At the same time, positively charged ions of hydrogen from the acid remove free electrons from the copper plate, which becomes positively charged. Through a conducting material connecting the plates, free electrons move from the zinc plate to the copper plate as long as the chemical reaction lasts.

Dry cells also develop electric potential via chemical actions within the cell. Free electrons removed from the carbon rod collect on a zinc can. The rod exhibits a positive charge and the can becomes negatively charged; this allows for an electric potential to develop between these two items. Through a conducting material connecting the can to the rod, free electrons move from the can to the rod as long as the conducting path exists.

Electric generators develop an electric potential via magnetic induction. Moving a conducting rod through a magnetic field that exists between the poles of a horseshoe magnet causes an electric potential to be set up in the rod. Free electrons move through this rod from one end to the other for as long as movement of the rod is maintained. The direction of this movement depends on whether the rod is moved across the lines of force in the magnetic field in either the opposite direction or the same direction. Generators usually consist of multiple conductors mounted on a cylinder that rotates in a magnetic field.

Thermocouples utilize heat to develop an electric potential. Two strips of different metals are connected at one end to form a junction and the other ends are kept apart. A heat source is applied to the junction; this causes each metal strip's temperature to rise at the junction. The free ends aren't as hot and electric charges are produced at these free ends. Because the strips consist of different materials, there's a difference of potential between these free ends; when connected by a conducting wire, the electrons can move through the pathway. The voltage that's produced will become greater as the difference in temperature between the free ends and the junction increases.

a. Increase

b. Decrease

c. Decrease

Since 1 Btu = 0.293 Wh, dividing the given amount of Wh by 0.293 will convert this amount into Btu. Therefore, 0.8 : 0.293 = 2.73 Btu

365 days * 10 hours * 40 W = 146,000 Wh or 146 kWh

Explanation:

Penn Foster