P3 Flashcards
What is a conductor
material that allows flow of electric current through it
What is a insulator
material that does not allow flow of electric current through it (e.g. wood, plastics, glass)
What is an electric field
A region in which an electric charge experiences a force
What is a current
the flow of charge per second
What is voltage
- energy transferred per coulomb of charge that passes
- measured between two points in a circuit.
What is electrical motive force
- electrical work done by source
- in moving unit of charge around complete circuit
What is a Parallel circuit
circuit in which the voltage across each component is the same (current likely to differ)
What is a series circuit
circuit in which the current through each component is the same (voltage likely to differ)
What is a charge
A property of matter which is positive or negative
What is resistance
- measure of the difficulty of passing an electrical current through material
- Calculate from Resistance = voltage (or p.d.)/current
What is Ohm’s law
- voltage across a component directly proportional to current through it
- provided the temperature remains constant
What is Conventional Current
The current that (theoretically) flows from the positive side of the battery to the negative.
What is Real Current Flow
Referring to the actual flow of electrons from the negative side of the battery to the positive.
What is Electrical energy
Transfer of energy allows work to be done within a circuit. Measured in Joules.
What types of charges exist
postive and negative
What happens when opposite charges are introduced
they’re attracted
What happens when similar charges are introduced
they repel each other
Why are conductors able to conduct
allows negatively charged electrons to flow through it
Why do insulator prevent conduct
does not allow electrons to flow. Electrons are still present in an insulator but are normally stationary or “static”
What is static electricity
accumulation of charge
How does static electricity occur
When 2 insulators rub against each other
What can friction cause
electrons to be removed from the surface of an insulator leaving it positive
What can be also a possibilty due to friction
Electrons to be added surface of an insulator making it negative, because there are now more electrons than protons.
What does charging an object mean
adding or removing electrons
EXamples of conductors
silver, gold, steel, aluminium, and others
EXamples of insulators
Plastic, wood, e.t.c
State a simple experiment on electrostatic charges by friction
Rub a balloon on your hair for about 30 seconds
Hold the balloon near small pieces of paper or a hair strand
Observe how the paper or hair is attracted to the balloon
Interpretation:
Friction between the balloon and hair transfers electrons from the hair to the balloon, making the balloon negatively charged
The negatively charged balloon attracts the positively charged paper or hair, demonstrating electrostatic attraction
What do electric circuits do
transfer energy from one place to another using moving charges
What are 4 components of a circuit
a source, a load, conductors/wires, and a switch
What function does a source do
puts electrical energy into a circuit there are 2 common types a cell and a battery
what is a load p3
components or devices that use the electrical energy and convert it into another form. For example a bulb, resistor, heater, e.t.c
What are the functions of a conductor
connect the components. We assume that they have no resistance and electricity flows easily through them
what function does a switch have
controls the flow of electricity
What loop is required for electricity to flow
a close loop where the wires connect to the negative and positive end of the source
What qualifies as a series circuit
When there’s only one path for the charges to follow
What qualifies as a parralel circuit
there are multiple paths for the current to flow. You will see junctions in the circuit. Junctions being where charges join together
How are circuits analyzed
In conventional current flow where we assume that charges come from the positive end of the source
What units are charges in
C, coloumbs it’s what electrons carry
What units is a current in
A, amps the rate flow of charges
how to find current of a circuit
charge/time
What is shortened formula for current
I=Q/t
What increases a current
- more coloumbs of charge travelling
- less time taken for charge to travel through circuit
What does an ammeter measure
the current of a circuit
How to attach an ammeter to a circuit
connect it in series of the circuit before the load
Is the current equal at all times in a parralel circuit
no the current at the source is larger than the current at each branch off to the load
WhaWhat is unique property for parralel circuit currents
the current at the source is the sum of the currents of the branch
What is potential difference
work done by unit of charge passing between two points in circuit
Difference between potential differnce/voltage and emf (electromotive force)
Emf: amount of energy supplied to coulomb of charge by power source in driving the charge around a complete circuit.
Potential difference across a component is the amount of energy supplied to a component by a coulomb of charge
What do voltmeters measure and how to attach to circuit
The potential difference of charge before and after component. It should be attached in parralel this allows it to compare the charges
What is resistance exactly
measure of difficulty of passing electical current thru material
What is ohms law
- voltage across component directly proportional to current thru it
- provided temp remains constant
What affects resistance
A high voltage increases resistance, a low current increases resistance
Difference in current-voltage graph of a filament lamp and resistor
The resistor shows that
Current directly proportional to voltage
Straight line graph, goes through origin, fixed value for gradient - gradient equals resistance
The filament lamp
Current NOT directly proportional to voltage
Curved graph, goes through origin, gradient increases as current increaseg
This is because the filament lamp becomes hotter which increases resistance of charges
What relationship does length of wire have with the resistance of the wire
the longer it is the more resistant it is directly porportional
What relationship does cross sectional have with the resistance of the wire
the smaller the cross sectional area the larger the resistance. they have a inversely porportional relationship
What happens when you put two resistors in series
their resistance increases leading to a lower current
What happens when you put two resistors in parralel
their resistance decreases leading to a higher current
