Unit D Electrical Principles: 1.0 & 2.0 Flashcards
What causes static electricity?
The proton has a positive charge and the electron has a negative charge. The charges on the particles can cause either attractive or repulsive forces between the particles
Why do objects attract or repel each other?
Because they are electrically charged
same sign repels, and different sign attracts
So electrons can push other electrons away for example
How do opposite charges affect each other?
They attract each other
How do like charges affect each other?
They repel each other
What makes an object neutral?
having equal amounts of positive and negative charges
What do charged objects cause when they are brought next to neutral objects?
Charge separation
What does it mean if an object is charged?
They either have more protons than electrons or the opposite.
What is charge separation?
When protons or electrons on a charged object cause it to repel on neutral objects
What is electrical discharge?
When a negative charge builds up on an object and causes it to be attracted to another object and so it jumps to that object.
What are the laws of electrical charges?
- Opposite charges attract each other.
* Like charges repel each other.
What are VAN DE GRAAFF GENERATORS?
A machine that produces static build-up by using friction
How does a Van De Graff generator work?
A rubber belt rubs on a piece of metal and transfers the charge to a sphere. The charge builds up on the sphere and transfers to you when you touch the sphere
How is electricity in an electric eel produced?
By a special organ in the tail that contains thousands of modified muscle cells called electroplaques
Why are static charges not able to operate electrical devices?
They build up and discharge, but they do not flow continuously.
What is electrical current?
The steady flow of charged particles
What are the two conditions that let electricity flow continuously?
-The flow of electrical current requires an energy
source
- Electrical current will not flow unless it has a complete path or circuit for the charged particles to flow through
What are amperes?
The rate at which an electrical current flow is measured
Who is the ampere named after?
in honour of the French physicist, mathematician, and philosopher André-Marie Ampère
What are materials that electrical charges can move through easily called?
Conductors
What is a circuit?
A circuit is a path that controls the flow of electricity
What is a load in a circuit?
The load is a device to convert electrical energy to another form of energy
What does a circuit usually include?
A circuit usually includes a conductor, an energy source, and a load
What is Electrical energy?
The energy carried by charged particles
What is voltage?
Voltage is a measure of how much electrical energy each charged particle carries
What is voltage also called?
Potential difference
The higher the voltage is, the greater the ……
potential energy of each particle.
What is the unit of voltage?
The unit of voltage is the volt
What is the simplest way to measure volts?
The simplest way to measure voltage is with a voltmeter.
What is each millivolts to volts?
Each millivolt is 1/1000 of a volt
What does short circuit mean?
When it bypasses part of the normal circuit
What must be considered if you get an electric shock?
voltage and amperage
What is most important when assessing the danger of an electric shock?
The number of amps is much more important than voltage
What would happen if 0.001 A passed through your body?
You would likely not feel it
What would happen if 0.015 A to 0.020 A passed through your body?
You will cause a painful shock, and loss of muscle control.
What is the third prong in the plug meant for?
It connects to the ground of your home just in case it short circuits
How do fuses work?
Fuses contain a thin piece of metal that is specially designed to melt if too much current passes through it.
How does a circuit breaker work?
Instead of melting, the hot wire triggers a spring mechanism that turns off the switch inside the circuit breaker. As soon as the wire has cooled, the circuit breaker can be turned back on
What is a lightning rod?
A rod on a tall building that connects to the ground in case lightning strikes
What does a pacemaker do?
Delivers a small amount of current at regular intervals to keep the heart beating normally
What is an electrochemical cell?
An electrochemical cell is a package of chemicals designed to produce small amounts of electricity
Where does the electricity in a electrical cell come from?
Chemical reactions between the different metals
What are the 2 different types of cells?
Dry cells and wet cells
Why are dry cells called dry cells?
Becuase they are in a paste and sealed so they can be used in any position
How does a dry cell work?
The chemical reaction in the cell releases free electrons. These electrons travel from the negative terminal of the cell, through the electricity-using device, and back to the positive terminal of the cell
What is an electrolyte?
An electrolyte is a paste or liquid that conducts
electricity because it contains chemicals that form ions
What is an ion?
An ion is an atom or a group of atoms that has become electrically charged through the loss or gain of electrons from one atom to another
What are the 2 metals in a cell called?
Electrodes
What happens as a result of the electrodes reacting with the electrolyte?
As a result of this reaction, one electrode becomes positively charged, and the other becomes negatively charged
What type of electrolyte does a wet cell use?
Usually an acid
How does a wet cell work?
The acidic electrolyte gradually eats away the zinc
electrode. This process leaves behind electrons that give the slowly disappearing electrode a negative charge. Eventually the zinc electrode must be replaced. The chemical reaction between the copper electrode and the acidic electrolyte leaves the copper with a positive charge but does not eat away the copper. Electrons travel along the wire from the negative zinc electrode to the positive copper electrode
What are primary cells?
Primary cells produce electricity from chemical reactions that cannot be reversed. E.g. Dry cells and wet cells
What is different about a rechargeable cell?
The chemical reactions in a rechargeable cell can be
reversed
How does a rechargeable cell work?
By using an external electrical source to run electricity back through the cell. The reversed flow of electrons restores the reactants that are used up when the cell produces electricity.
What are secondary cells?
Cells that can be recharged
What creates a battery?
Connecting cells together
What is electrolysis?
Using electricity to split molecules into elements
What is electrochemistry?
The study of chemical reactions
What are common uses for electrolysis?
To make drinking water safe, and to make rocket fuel
What is electroplating?
Covering cheaper metal with a more exspensive metal
How does electroplating work?
Using a wet cell. The item to be coated and a bar of the coating are immersed in an electrolyte. A source of electricity is connected between the two metals. The flow of electricity deposits atoms from the positive metal to the naegative metal.
What is Electrorefining?
Used to remove impurities from metal
What is Anodizing?
A process to coat aluminum part with a layer of aluminum oxide
Describe neon signs
Consist of a glass tube filled with gas. The tubes have metal on each end and connected to an electrical source
How do electrons look in insulators?
The electrons are tightly bound to the nuclei so they resist movement
How do electrons look in a conductor with no voltage applied?
The electrons are not as tightly bound to the nuclei. They can drift away from the nuclei but do not flow in any one direction.
How do electrons look in a conductor with voltage applied?
They are not bound to any nuclei. The electrons flow toward the positive terminal of the voltage source.
What are superconductors?
Superconductors are perfect conductors—they have no resistance to electron flow
Why aren’t all metals superconductors?
Becuase the electrons encounter resistance
What is required for mercury to be a perfect conductor?
Must be cooled to absolute 0 (-273 C)
What is a resistor?
A resistor allows electric current to pass but provides resistance to it. This limits the amount of current.
What is Resistance?
Resistance is a measure of how difficult it is for electrons to flow through a substance
What is resistance measured in?
Ohms
What can increase the energy a substance gains?
Resistance
Why is distilled water not a good conductor?
Because it only contains water molecules and they have no electrical charge.
How does a lie detector machine work?
It uses the salt in your sweat. If you sweat more you conduct more electricity
How does a switch work?
When a switch is on two conductors are pressed together to complete a circuit
What is a variable resistor or rheostat?
Rheostats can increase or decrease the amount of current in a circuit by adjusting the portion of the resistor that the current travels through
What kind of wire in a circuit would have more resistance?
A long thin wire
What decreases if you add resistance?
current
What is ohms law?
Ohm’s law states that as long as the temperature stays the same:
• the resistance of a conductor stays constant, and
• the current is directly proportional to the voltage applied.
What is the formula for find the voltage, resistance, or current of a circut?
I x R
Who created ohms law?
Georg Simon Ohm
Why is ohms law not perfect?
Becuase the temperature of a resistor changes the resistance changes as well
What is potential difference sometimes called?
Voltage drop
How is potential difference measured?
Using voltmeter or milivoltemeters
What are ammeters used to measure?
Ammeters are used to measure electric current in amperes
What are galvanometers?
Meters used to measure small currents are sometimes called galvanometers.
What are multimeters used to measure?
Voltage, current, or resistance in a circuit.
What are the four parts of a circuit?
- Energy Source
- Conductor
- A switching mechanism
- A load
What are the two different types of circuits?
Parallel and series circuit
Explain a series circuit
In a series circuit, there is only one pathway for the current. If that pathway is interrupted, the whole circuit cannot function
What are the problems with a series circuit?
- If a pathway is interrupted, the whole circuit cannot function.
- adding components increases the total resistance of the circuit. Which decreases current
Explain a parallel circuit
They have a separate current path for each section of the circuit
What are some positives to parallel circuits?
- An interruption or break in one pathway does not affect the rest of the pathways in the circuit
- Adding a new pathway with more resistors does not affect the resistance in any of the other pathways
What are microcircuits?
Circuits on an extremely small scale
