Chapter 10 Electrical Circuits Flashcards
What’s Kirchoffs second law?
The sum of emf is equal to the sum of p.d. around a closed loop
What is a series circuit?
one path for current a single loop from one terminal to the other
What is current in series circuit?
Current is the same everywhere
How is emf shared in resistors in a series circuit?
If resistance is the same emf is shared equally
What is a parallel circuit?
it provides more than one possible paths for the charges
How do you add resisitors in series?
Total resistance is equal to each individual resistors added together.
R(total) = R(1) + R(2) …
How do you add resistors in parallel?
1/R(total) = 1/R(1) + 1/R(2) …
what is the relationship between emf terminal p.d. and lost volts?
emf = terminal p.d. + lost volts
what is terminal p.d.
the p.d. measured at terminals of the power source
What is the internal resistance equation?
𝜺 = 𝑰(𝑹 + 𝒓)
What is internal resistance in a terminal p.d againt current graph?
the negative gradient
How does the voltage across a component in a
potential divider correspond to its resistance?
V/VT = R/RT
What is the purpose of a potential divider?
To provide variable potential difference, or to
provide a constant specific potential difference
Describe an experiment to determine the internal
resistance of a source.
Set up a circuit with a source, ammeter and variable resistor in series, and a
voltmeter in parallel.
Vary the resistance and measure the voltage and current (take several readings).
Plot a V-I graph.
V = -rI + ε corresponds to y=mx+c
The internal resistance = -m (-gradient).
What are ‘lost volts’?
‘Lost volts’ refer to the difference in voltage
between that supplied by the source and the
amount available to the circuit.
