Plz help asap. 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?

Not my answer but nevertheless

Electric potential develops in primary/dry cells through a chemical reaction between the cell plates of the cell. free electrons move from the zinc plate to the copper plate through a conducting material.  

Electric potential develops in Generators via magnetic induction i.e. the movement of a conducting rod through the magnetic field between the poles of the horseshoe magnets produces Electric potential in Generators.

Electric potential develops in thermocouples via heat transfer ; A heat source is applied to the connecting end of the thermocouple strips and this will cause the production electric charges ( potential ) at the free ends

3) Identifying effect of each scenerio

a) The resistance of an electric current will increase when the length of the conductor increases

b) The resistance of an electric current through a body will decrease when the conductor has a larger cross-section

c) The resistance of an electric current through a body will decrease when the temperature of the conductor is cooled

4) The amount of heat lost as heat in Btu = 2.73 Btu

amount of heat lost = 0.8 Wh

convert to Btu = 0.8 Wh / 0.293 = 2.73 Btu   ( note : 1 Btu = 0.293 Wh )

5) The amount of of energy used by a 40 W bulb for 365 days = 146 kWh

Power of bulb = 40 W

Run time = 10 hours * 365 days

∴ amount of energy used = 3650 * 40 = 146 * 10^3 Wh = 146 kWh

a.metals can become magnetic if they have many spinning electrons that create magnetic fields.d.only some metals are attracted by magnets; these metals are called ferromagnetic.

d.wrapping an insulated wire around a metal with ferromagnetic properties and applying an electric current.

the minimum amperage that the current in this wire would have to have so that its weight is completely supported by the magnetic force due to earth's field, assuming that no other forces except gravity act on it