Physics Revision Term 1 test (5/3/18)

Pregunta	Respuesta
What is conventional current flow?	Positive to negative charge
What is the formula to work out resistance in series?	RT = R1+R2...+RN
The unit of charge	q, the coloumb
Properties of current	Unit: I The number of electrons per second carried through a conductor
Properties for voltage	Unit: V The potential difference between negatively charged and positively charged objects
Properties of resistance	Unit: R Property of material that helps prevent the flow of electrons in it.
What is static electricity?	Static electricity occurs when there is a build up of electric charge on the surface of a material.
Why is static electricity so called?	Static electricity is so called because the charges don't move. The electricity we use everyday involves moving charges.
How is static electricity caused?	Static electricity is caused when certain materials are rubbed against each other and electrons are stripped off.
What do electrons have to do with static electricity?	Electrons are stripped off one material and onto another.
Materials with extra electrons...	...are negatively charged.
Materials that have lost electrons...	...become positively charged.
What are the 2 types of current (acronyms and names)?	DC - Direct Current AC - Alternating Current
Where is AC current commonly found?	In power sockets in the wall.
Give one example (probably the main example) of where direct current is used	Main example: Batteries
Alternating current	Flow of charge back and forth, changing its direction many times in a second (50-60 Hz)
Direct Current	Flow of charge always in one direction
1 Hertz (Hz)	1 Hertz (Hz) = 1 cycle per second
The Central Concept	Closed circuits
Ohm's Law states that:	Ohm's Law states that electric current flowing through a wire is directly proportional to the potential difference across its ends, provided its temperature remains the same.
What does 'directly proportional' mean?	Directly proportional means if one variable is always the product of the other variable and a constant. eg) Voltage (V) is variable 1 Current (I) is variable 2 Resistance (R) is a constant (K) Variable 1 = Variable 2 x constant Voltage = Current x Resistance V = IR Hence Ohm's Law
In a parallel circuit, current is...	...split
In a series circuit, voltage is...	...split
In a series circuit, current...	...remains the same
In a parallel circuit, voltage...	...remains the same
Another equation for current is:	I = Q/t (total charge per second)
In the equation I = Q/t, what does each variable mean?	I = Current Q = Total charge t = time
Another formula for voltage is:	V = w/q (joules per charge)
In the equation V = w/q, what does each variable mean?	V = Voltage w = work done, energy, joules q = charge
List as many formulas for POWER as you can:	More common formula: P = w/t, or work done divided by time (seconds) Also known as joules per second. Other formulas for Power: P = VI (watts) P = w/t (watts) P = V squared / R P = R x I squared P = F.d/t (work done/energy) or P = F x V
What does Kirchhoff's 1st Law state?	The sum of total current equals to 0 eg) I (in) = I1+I2+I3...+IN
What does Kirchhoff's 2nd Law state?	The sum of total voltage equals 0. eg) V (in) = V1+V2+V3...+VN Each path in a parallel circuit is one loop for voltage. eg) There are 4 paths in a parallel circuit. The voltage in each path is 12 volts. One path is therefore 12 volts. With that being said, in series, voltage is split, so if there are 2 equal resistors in the now series path, the voltage will split up into 6 volts each. If the resistors are of different value, the voltage will vary, however, they will always add up to 12 volts at the end of the circuit.
Explain how VI = w/t using other known formulas	V = w/q I = Q/t therefore P = w/q x Q/t = w/t therefore VI = w/t OR V = w/q therefore w = Vq I = Q/t therefore t = Q/I So P = w/t = Vq x I/Q = VI therefore VI = w/t
Unit for energy:	Joules (J)
Unit for time:	Seconds (s)
Unit for power:	Watt (w)

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