E.M.F And Internal Resistance Flashcards
[………] have an Internal Resistance.
Batteries
Resistance in metals comes from electrons colliding with 1-[………] and 2-[………] energy
1-Atoms (or ions)
2-losing
In a battery what kind of energy does it use to make electrons move?
Chemical energy
What is Internal Resistance?
Is when electrons collide with atoms inside the battery creating a resistance
Internal resistance is what makes batteries and cells [……..][….] when they are used.
Warm up
We assume wires have […….] resistance.
Zero
What is Load resistance?
Is the total resistance of all the components in the external circuit, can also be called ‘external resistance’
How does a battery produce energy?
By chemical reactions
What is the Electromotive force or E.M.F?
The total amount of work the battery does on each coulomb of charge.
What is E.M.F measured in?
Volts
What is the E.M.F equation?
ε = W / Q
ε = W / Q What is W?
Is the work done on the charge.
What is the Potential Difference across the load resistance?
Is the work done when one coulomb of charge flows through the load resistance. Is called the ‘terminal P.D’
What would the the Terminal P.D equal if there was no internal resistance?
Terminal P.D would be the same as the E.M.F
What is the energy that is waged by overcoming the internal resistance called?
Lost Volts
What is Lost Volts?
The energy water per coulomb overcoming the internal resistance
How does the conservation of energy law apply to Internal Resistance?
Energy per coulomb supplied by the source = energy per coulomb used in load resistance + energy per coulomb wasted in internal resistance
List 4 different E.M.F equations.
ε = V + v ε = I(R + r) V = ε - v ε = V + Ir
What does ε stand for?
E.M.F
What does V stand for?
Terminal P.D ( the p.d across the load resistance)
What does v ( little v ) stand for?
Lost volts
What does I stand for?
Current
What does R stand for?
Load resistance
What does r stand for?
Internal resistance ( resistance inside the battery )
How do you calculate E.M.F (ε) for multiple cells in series?
ε(Total) = ε(1) + ε(2) + ε(3)
Add their individual E.M.Fs together
How do you calculate the E.M.F for multiple IDENTICAL cells in Parallel?
ε(Total) = ε(1) = ε(2) = ε(3)
The total E.M.F of the combination of cells is the same size as the E.M.F of each of he individual cells
What is the independent variable?
The variable you change
What is the dependant variable?
Is the variable you measure
What is the control variable?
Is the variable you do not change
When investigating Internal Resistance and E.M.F what do we measure?
The P.D for servers different values of current
- Bart the current by changing the value of the load resistance with the variable resistor
When investigating Internal Resistance, what kind of graph do we plot?
P.D (y axis)
Current (x axis)
When measuring Internal Resistance and E.M.F what equation do we rearrange?
ε = V + Ir
When investigating Internal Resistance and E.M.F - what do we rearrange ε = V + Ir to give?
V = -rI + ε
When investigating Internal Resistance and E.M.F, what part of V = -rI + ε are constants?
ε & r
When investigating the Internal Resistance and E.M.F, what does the y-intercept equal on a P.D (y axis) to Current (x axis)?
Y-intercept = ε
When investigating Internal Resistance and E.M.F, what does the gradient on a P.D (y axis) to Current (x axis) equal?
Gradient = -r
