Electromotive Force

Question 1

what is the definition of an electromotive force of an electrical source

Answer 1

• the energy converted into electrical energy by the source

- per unit charge

Question 2

what are the differences between what kinds of energies are transferred in a cell and alternator

Answer 2

• in a cell, chemical energy is converted into electrical energy
• whereas in an alternator, mechanical energy is converted into electrical energy stores

Question 3

where would you see an alternator for example

Answer 3

in the engine of a car

Question 4

what is the common ground between a cell and an alternator if they convert different types of energies

Answer 4

they are both producers of an electromotive force

Question 5

why is the name electromotive force actually misleading

Answer 5

• because what is actually going on has nothing to do with forces
• it is all about energy transfers and conversions

Question 6

what is the abbreviation of electromotive force

Answer 6

e.m.f or a backwards 3

Question 7

of the e.m.f. of an electrical source is the energy (eg, chemical) per unit charge converted into electrical energy, what word equation can be written for this

Answer 7

e.m.f. = energy converted into electrical energy / charge passing

Question 8

what would be the symbol equation for e.m.f.

Answer 8

• energy transferred = work done
• charge passing = charge
• so e.m.f. = W / Q

Question 9

what are the units for e.m.f. and why

Answer 9

• it is the same equation for p.d.
• so its units are JC^-1
• and it is therefore measured in volts (V)

Question 10

what is a simpler definition of e.m.f.

Answer 10

• the creation of electrical energy

- from other forms of energy

Question 11

what relationship can you make between e.m.f. and p.d. now that you know both their roles

Answer 11

• emf and pd have a cause and effect relationship
• emf is the cause and pd is the effect
• this is simply because emf is the CREATION of electrical energy from other energy forms (what actually creates the pd and electric field)
• while pd is the CONVERSION of electrical energy into other forms (what causes the electrons or charge carriers to move and make magic happen)