Deck 4: Sensing 3

Question 1

Explain why objects have resistance?

Answer 1

Resistance comes from electrons colliding with atoms and loosing energy.

Question 2

Where do you find internal resistance?

Answer 2

In a battery

Question 3

What is load resistance?

Answer 3

Load resistance is the total resistance of all the components in the external circuit. Might also be called “external resistance”.

Question 4

What is electromotive force? (e.m.f)

Answer 4

The amount of electrical energy the battery produces for each coulomb of charge is called the e.m.f.

Question 5

What is the potential difference across the load resistance in a circuit?

Answer 5

The energy transferred when one coulomb of charge flows through the load resistance. This potential diffirence is called terminal p.d.

Question 6

If a battery has zero internal resistance what would the terminal p.d be?

Answer 6

The terminal p.d would be equal to the e.m.f.

Question 7

Give the four different e.m.f formulas.

Answer 7

1) E=V + v 2) E=I(R+r) 3) V= E - v 4) V = E - Ir

Question 8

Explain why a car would need a low internal resistance?

Answer 8

A car battery has to deliver a really high current- so it needs a low internal resistance.

Question 9

What does HT and EHT mean and what are they designed for?

Answer 9

• HT(high tension) and EHT(extremely high tension) supplies are designed with high internal resistances. This means that if they accidently short-circuited only a very small current can flow- much safer.