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Topic 3: Electric Circuits (Quiz)
Terms in this set (33)
What is electricity?
A means of transferring energy (not energy itself)
What is the present model of electric current?
The flow of charged particles
What are the SI units of charge?
What are the SI units of current?
What is 1C equal to?
1As - the current passing a given point in a wire when a current of 1A flows through the wire for 1s
How many electrons carry one coulomb of charge?
6.25 x 10^8 electrons
What is the area under the line of a current-time graph?
What makes up the current in metals?
Free electrons carrying a negative charge
Is an electric current always a flow of electrons?
No - it is the flow of charged particles
What are the charge carriers in an electrolyte?
Positive and negative ions
By convention, which way does the electric current flow?
In the direction of the flow of positive charge, so the electrons flow one way around a circuit while conventional electric current flows in the other
What are the units of emf?
When is a cell said to have an emf of 1V?
When it supplies 1J of energy to each 1C of charge flowing through it (1V = 1J/C)
Given that the physical factors (including temp) stay the same, what is current proportional to?
the potential difference across its end
What does the resistance of a uniform conductor depend on?
- Length (l)
- Cross sectional area (A)
- the material it is made of
What are the SI units of resistivity?
What is an example of an ohmic conductor?
A metal at a constant temperature
How may temperature change result in superconductivity?
When some materials are cooled to a very low temperature, superconductivity may result
Which metals exhibit superconductivity?
Mercury, Many compounds and alloys
What is power dissipation measured in?
What does Kirchhoff's First law state?
The total current into any point in a circuit is equal to the total current out of that point - as a result of the conservation of charge
What does Kirchhoff's Second law state?
The sum of potential rises and falls around a closed path in a circuit is zero - as a result of the conservation of charge
When do falls in potential occur?
Where energy is transferred FROM the flowing charge
When do rises in potential occur?
Where energy is transferred TO the flowing charge
What is the volume control knob on a music system an example of?
A potential divider
What are potential dividers used for?
In circuits that sense changes using devices such as light-dependent resistors and thermistors
What is the potentiometer?
a resistor with a sliding or rotating contact that forms an adjustable voltage divider
What are the two effects of the internal resistance of such a source?
1. Results in the voltage across the terminals (terminal potential difference) of the source drop as a current is drawn from it
2. energy is dissipated in the internal resistance from the source as current flows through it
What is the open circuit voltage?
Voltage given on a source of emf (e.g. battery) is the voltage measured when no current is being drawn from it
How do you find the total e.m.f of multiple cells in series?
By adding the individual e.m.f.s
How do you find the total e.m.f of multiple cells in parallel?
the total e.m.f of the combination of cells is the same size as the e.m.f of each individual cells
What is the resistance of a voltmeter?
Voltmeters have a very high resistance, but a small current will still flow through them.
There will still be some lost volts, which means that the value is slightly less than the e.m.f. (usually insignificant)
What is 1 coulomb equivalent to?
One coulomb is equivalent to the current passing a given point in a wire when a current of 1A flows through the wire for 1s
1C = 1As
THIS SET IS OFTEN IN FOLDERS WITH...
Topic 2: Mechanics
Units and Conversions (Physics)
Topic 4: Materials
Topic 4: Materials (Quiz)
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