2.4 Electromotive force

 $r$  

• emf

• p.d.

• internal resistance

• lost volts

 $\epsilon$  

• electromotive force

• potential different

• internal resistance

• potential drop

 $Ir$  

• electromotive force

• potential difference

• internal resistance

• potential drop

Which is a true statement?

• No sources of emf have internal resistance

• Some sources of emf have internal resistance

• Most sources of emf have internal resistance

• All sources of emf have internal resistance

The gradient on a  $V-I$  graph is 

•  $r$  

•  $-r$  

•  $\epsilon$  

•  $-\epsilon$  

The V-intercept on a  $V-I$  graph

•  $r$  

•  $-r$  

•  $\epsilon$  

•  $-\epsilon$  

What is emf?

• the electro motive "force" or the force on electrons

• the electromotive "force" or the Voltage of a cell measured when there is no current flowing

• the electromotive "field" or the Voltage of a cell measured when there is no current

• the electromotive "force" or Voltage of a cell measured when connected to a circuit

What is internal resistance?

• the resistance inside the cell that increases with more current drawn from the cell

• the resistance inside the cell that decreases with more current drawn from the cell

• the resistance inside the cell that remains constant as the current drawn from the cell changes

• the resistance inside each component which increases as more resistances are added in series

The gradient of this line represents the

• internal resistance

• emf of the cell

• power of the cell

• resistance of the circuit

Correct

•  $\epsilon=V+Ir$  

•  $\epsilon=I\left(R+r\right)$  

•  $\epsilon=V$