Topic 3 - Electric Circuits Flashcards
current
rate of flow of charge
what is the gradient on a charge time graph?
Current ( I = Q/t)
how do you work out charge in a current-time graph ?
area under the graph (Q = It)
An Ammeter must…
have a low resistance and must be placed in series
A voltmeter must…
have an infinitely high resistance and must be placed in parallel
another word for voltage is…
emf / potential difference
potential difference is…
a measure of the amount of energy or unit of charge transferred between 2 points in a circuit
what is Kirchoff’s first law?
the total current flowing into a point is equal to the current flowing out of that point. Conservation of Charge
what is Kirchoff’s second law?
around any closed loop in a circuit, the sum of the pd across all the components is the pd of the supply. Conservation of energy.
power(watts) is…
rate of transferring energy/ rate of doing work.
1 watt of power means…
1 joule of energy is used every second
ohms law:
V = IR
in a series circuit the current is…
the same across all the components
in a parallel circuit the current…
total current = is the sum of the current in all the branches
potential difference in a series circuit…
total of = sum of pd in all appliances
potential in parallel circuits is…
the same across each branch
resistance in a series circuit…
total resistance = the sum of the resistance in all the components
resistance in a parallel circuit…
reciprocal of Resistance = is the the sum of all the reciprocals of the resistance of all the components
is a resistor a conductor?
yes, it’s a conductor so that current can still flow around a circuit however resistors let less current flow than other conductors
what effects the resistance of a resistor?
cross sectional area of the wire
length of the wire
material of the wire
temperature of the wire.
what is resistance proportional to?
Length
What is resistance inversely proportional to ?
Cross-Sectional Area
What is the Resistivity?
The resistance of a 1m² 1m long sample (the resistance per unit cube). its a property of a material.
The resistivty is constant providing…
the temperature is constant