Electricity

Question 1

What is kirchoffs 2nd law?

Answer 1

Sum of EMFs around any loop is equal to the sum of the P.Ds

Question 2

What is kirchoffs 1st law?

Answer 2

At any junction, sum of current in is equal to sum of current out.

Question 3

Explain EMF

Answer 3

emf = energy per unit charge.

Question 4

Explain internal resistance

Answer 4

The resistance to flow of current inside the power supply itself, consider it as a resistor of resistance r in series with a p.d of magnitude e.

Question 5

Write some EMF equations

Answer 5

emf = IR + Ir, terminal volts + lost volts. V = emf - Ir, terminal P.D = emf - lost volts.

Question 6

Give equations for cells connected in parallel.

Answer 6

If no internal resistance, total p.d is p.d of one of the cells, and current is the same for just one cell. If there is internal resistance for n cells, current is I/n; lost p.d = Ir / n, terminal P.D is V = emf - (I/n)r, so acts as a source of emf e and int. resistance r/n.