Internal Resistance and EMF

Question 1

in a battery what type of energy store is used to make electrons move?

Answer 1

Chemical energy

Question 2

What is the resistance caused inside the battery called?

Answer 2

internal resistance

Question 3

What does interna resistance cause to happen (physical sensation of battery)

Answer 3

makes it warm

Question 4

Definition of internal resistance

Answer 4

opposition to flow of charge through the cell, causing energy dissipation in wires.

Question 5

What is the lost volts?

Answer 5

work done in pushing electrons through the cell against the internal resistance

Question 6

What does EMF stand for

Answer 6

electromotive force

Question 7

What is emf?

Answer 7

the work done per unit charge to create electrical energy from other energy stores (for example chemical)

Question 8

What is the name of the resistance within the circuit?

Answer 8

load resistance

Question 9

What are lost volts?

Answer 9

energy lost per coulomb overcoming the internal resistance

Question 10

Equation for emf?

Answer 10

work done / charge

Question 11

Equation 2 for emf (includes internal resistance)

Answer 11

E = V + v 
or 
E = I(R + r) 
or 
E = V + Ir

Question 12

What is the load resistance?

Answer 12

Resistance within the circuit

Question 13

How does emf behave in parallel and series?

Answer 13

The same as the pd

Question 14

How can we determine emf and internal resistance?

Answer 14

Set up a circuit consisting of a cell , ammeter and a variable resistor . Also a voltmeter in parallel.

• we vary the current using a variable resistor
• measure pd for each current
• Record
• E = V+ Ir, plot using y = mx+c
• y - intercept = emf
• gradient = NEGATIVE internal resistance

Question 15

what is another way of measuring the emf?

Answer 15

connecting a voltmeter in parallel to the cell or battery

Question 16

Why is this method not always effective?

Answer 16

There will be some lost volts and hence the reading will be smaller