3.3 Flashcards
What is internal resistance?
The resistance (opposition of flow of current) that occurs within a cell or battery when current is flowing in a circuit.
What is electromotive force (emf)?
the energy gained by one coulomb of charge passing through a battery.
What is lost volts?
when there is internal resistance provided by the battery, a voltage is created over this resistance. This voltage is not available to the circuit and is called lost volts.
What is terminal potential difference (Vtpd)?
the voltage across the ends of the cell/battery when a current is flowing in a circuit
Break down the equation
E = Vtpd + Vl
E - electromotive force (V)
Vtpd - terminal potential difference (V)
Vl - lost volts (V)
Break down the equation
E = Vtpd + Ir
E - electromotive force (V)
Vtpd - terminal potential difference (V)
Ir - internal resistance (Ohms)
Break down the equation
E = I(R + r)
E - electromotive force (V)
I - current (A)
R - external resistance (Ohms)
r - internal resistance
Describe an experiment to measure EMF and internal resistance of a cell
- Set up a circuit as shown in the diagram
- Set the resistance of the variable resistor to a low level and measure the current on the ammeter and voltge on the voltmeter
3.increase the resistance of the resistor multiple times and record the current and voltage at each resistance. - plot each of these values on a voltage-current graph and draw a line through these points. The point where the line of best fit crosses the y-axis (when the current is 0) is equal to the EMF
- Calculate the gradient to get the negative of the internal resistance of the cell
What is the open circuit potential?
the potential difference that exist in an open circuit, where the current is 0
Draw a graph to show the relationship between terminal potential difference and curremt when a variable resistor is in the circuit.
