Chapter 12 - D.C Circuits

Question 0

What happens to the current in a parallel circuit?

Answer 0

The current from the cell divides into two portions I1 and I2

Question 1

Summarise a series circuit

Answer 1

• The current is the same at all points around the circuit
• The p.d. Add up
• The e.m.f. Add up
• The resistances add up

Question 2

What is the voltage in a component connected in a parallel circuit?

Answer 2

They have the same p.d across them

V1 = V2

Question 3

What is the formula when two resistors are connected in parallel

Answer 3

1/R = 1/R1 + 1/R2

Question 4

What is the other formula you can use for two resistors in parallel? Hint product/sum

Answer 4

R1R2
R= ———-
R1 + R2

Question 5

For 3 or more resistors in parallel what is the equation used?

Answer 5

1/R = 1/R1 + 1/R2 + 1/R3

Or

R=(R1+R2+R3*)-1

• means to the power of -1

Question 6

How is an ammeter connected? And why?

Answer 6

Ammeters are always connected in series, since they measure the current through a circuit. For this reason, an ammeter should have as low a resistance as possible so that as little energy is transferred in the ammeter itself. Inserting an ammeter with a higher resistance could significantly reduce the current flowing in the circuit.

Question 7

How is a voltmeter connected and why?

Answer 7

Voltmeter measures the potential difference between two points in the circuit. For this. They are connected in parallel (I.e between the two points) and they should have a very high resistance to take as little current as possible.