Studied by 7 people
Static & Electric Charge, Voltage, Circuits & Current, Resistance & Ohm's Law
What is static charge?
electrical charge that can be held in one place (static electricity)
How does static charge build up?
2 insulators rub together = friction → e- transferred through materials… now 1+ and 1-
What is an insulator material?
does not allow charges to move easily. ex: when one end becomes + the other will stay the same
What are examples of insulators?
glass, dry wood, ceramics, plastic, rubber
What is a conductor material?
allows electrons to travel freely.
Why are metals good conductors?
metal atoms have at least 1 valence e- that can transfer.
What material can retain static electricity?
Only insulators since it is held in one place
What are the properties of static charge?
never created/destroyed and charging = moving charge to different places
What is the unit of measurement for electrical charge?
Coulomb (C)
What is an electroscope?
detects static charge
What is a danger precaution about static charge?
Grounding = charge → Earth’s surface
What is a contact force?
apply force only on objects they touch (push/pull)
What are forces that act at a distance?
apply force without touching. Ex: gravitational, magnetic, electric force
What is an electric force?
a push or pull between charged objects
What are the laws of electric force?
1. Opposites attract
2. Same repel
3. Neutral is attracted to charged
What happens to the force if you increase the charge?
it is stronger
What happens to the force if the distance of charged increases?
it is weaker
What is Induction?
transferring electrons with no physical contact
What is conduction?
transferring electrons with physical contact
What is static discharge?
Static charge will dissipate, move into air moisture or spark
What is electric current?
electric charge moving though a wire
What is another name for voltage?
potential difference
What is voltage?
a measure in the difference of energy between two points
How and what is voltage measured in?
Voltmeter (outside circuit) and in volts (V)
When charges/electrons pass through a cell they…
gain potential energy (or the potential to do something)
What does an electrochemical cell do?
Converts chemical energy to electrical energy and gives electrons stored potential energy
What are the types of electrochemical cells?
Dry (flashlights) and wet (car)
What are the terminals?
electrodes = metal → anode (-) or cathode (+)
What is the paste/liquid solution in a cell called?
electrolyte
How does a battery produce voltage?
chemical reaction → charges separate in electrolyte but charges attract so it takes energy to pull apart = chemical →electrical energy = the potential for the electrons to move
What is energy and work and its unit?
energy is the ability to do work, work measures the transfer of energy, unit Joules (J)
What is an electrical current?
flow of electrons past a certain point within a time frame
What is current measured in and with what?
Ammeter (in series) ampres→amps (A)
If there is more electrons what is the current?
It is bigger
Does the current change within a circuit?
No
What are the circuit components?
source of electrical energy (cell/battery)
Conductor (wire)
Switch
Load = electrical energy →other forms of energy
What is resistance?
a measure of how much a material tries to stop electricity passing through it
How is there resistance?
electrons collide with metal atoms = vibration → heat
What is a resistor?
reduces current, (also use: transfer electrical energy to heat and light energy)
What affects resistance?
material
length
temperature - decrease = decrease in resistance
thickness - increase = increase in surface area → decreases collisions
What is the relationship between voltage and current?
Voltage increases = current increases
What is the relationship between resistance and current?
resistance decreases = current increases
What is Ohm’s Law?
Voltage = Current x Resistance
What is Ohm’s Law measured with and unit?
Ohmmeter, ohm (Lululemon symbol)
When there is a k before the unit… but when there is an m…
multiple by 1000…divide by 1000
What is a series circuit?
only one pathway for electricity to flow (no branches)
What is a parallel circuit?
more than 1 loop (multiple branches)
What is the formula for voltage in a series circuit?
V(source) = V(load 1) + V(load 2) + V(load3) + …
What is voltage in a series circuit?
each load loses a portion of total voltage, voltage across loads add up to total voltage supplied by battery/cell
What is the formula for current in a series circuit?
I(source) = I(1) = I(2) = …
What is current in a series circuit?
current at each part in circuit is equal to total current supplied by battery/cell
What is resistance in a series circuit?
more resistors = more resistance, if total resistance increases total current decreases
How do you find resistance in a question?
Use Ohm’s Law
What is the formula for voltage in a parallel circuit?
V(source) = V(load 1) = V(load 2) = …
What is voltage in a parallel circuit?
voltage is the same throughout circuit and equal to battery
What is the formula for current in a parallel circuit?
I(source) = I(1) + I(2) + I(3) + …
What is current in a parallel circuit?
divided into pathways that will rejoin , current through each pathway adds up to total current in the battery
What is resistance in a parallel circuit?
when resistors are placed in parallel = another pathway so total resistance decreases = current leaving battery increases
What are the 2 types of energy sources?
renewable = naturally replenished
non-renewable = can’t be replaced by natural means quickly enough to keep up with demand
How do generators work?
Fossil fuels → power stations → burnt = heat energy
Heat energy + water = steam
steam + turbines = generators
What are electrical generators?
a device to turn kinetic energy in turbines to electrical energy
How do electrical generators work?
magnet near wire = flow of electrons/electrical charge, electricity generated →cables → National Grid
How does coal create electricity?
powdered coal blown into furnace
coal burns = water heats in boiler
water → high pressure steam
steam turns turbine
turbine turns shaft connected to generator
generator turns = electricty
What is AC?
alternating current is electrical current produced by generators that can change direction. ex charging phone
What is DC?
Direct current is a source of portable electricity, ex. battery
How does DC work?
stores chemical energy that can change into electrical energy but cells might go flat (run out of chemical energy unless rechargeable
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