Test (Magnetism and Electricity) Flashcards
What is magnetism?
The force of attraction or repulsion caused by magnets
What is a magnet?
An object that can attract other objects containing iron, cobalt or nickel. ( Just because an object has these three qualities it doesn’t mean that they are magnets, they may attract one but aren’t a magnet themselves.)
What are the two opposite poles?
North and South
Opposite poles…
Same poles…
Attract
Repel
What is a magnetic field?
A magnetic field is the area of space in which the magnetic force of a magnet can act on another magnet.
What’s the movement of magnetic field lines?
Magnetic field lines always move out of the North end and into the South end.
Explain Ferromagnetism
When an unmagnetized substance is placed in a magnetic field, the substance can become magnetized. This happens when the spinning electrons lineup in the same direction.
The geographic…
North Pole is the magnetic South Pole
What does the magnet of the compass react to?
The magnet of a compass reacts to the Earth’s magnetic field to point to magnetic south, the geographic North Pole.
The arrow of a compass is attracted to which pole and repelled from which pole?
The arrow of a compass is attracted to the South Pole of a magnet and repelled by the North Pole of a magnet.
Describe live wires..
Live wires= current passing through They cause a magnetic field Have a conventional current The direction a positive particle would flow in a circuit From + to - end
Describe the right hand rule for the magnetic field of a live wire…
Point your thumb in the direction of the conventional current ( towards -). Your fingers are curling in the direction of the magnetic field around the wire.
What is a solenoid?
A solenoid is a cylindrical coil of live wire.
Describe how to figure out the magnetic field of a solenoid…
1) The fingers point in the conventional current direction on the coils.
2) The thumb shows the direction of the magnetic field lines (lines point North)
ALWAYS START PLUS IF SEEING OVER OR UNDER
What does electricity describe?
Electricity describes all the phenomena caused by positive and negative charges.
Electrical charges cannot be..
Electrical charges are not created or destroyed; they can ONLY be transferred from on object to another.
1) If the electrons=protons
2) If there are more electrons than protons
3) If there are more protons than electrons
1) neutral
2) negative charge
3) positive charge
What is a magnet?
An object that can attract other objects that contains iron, cobalt or nickel. ( Just because they have these three qualities does not mean they are magnets, they just have properties and can maybe attract a magnet but can’t pick anything else up.)
What are the two opposite poles?
North and South
Opposite poles…
Same poles….
attract
repel
What is a magnetic field?
A magnetic field is the area of space in which the magnetic force of a magnet can act on another magnet.
What’s a conductor?
A conductor is a substance that permits the free flow of electrical charges. (metals are usually conductors).
What’s an insulator?
An insulator is a substance that impedes the free flow of electrical charges.
(non metals are usually insulators).
What’s static electricity?
A stationary electrical charge that is built up on the surface of a material.
In what several ways can an object become charged?
Friction, Conduction and Induction
What’s friction?
When two objects are rubbed against each other, some atoms in one object may pull electrons away from the atoms of the other object.
What’s a static series?
When two neutral objects are rubbed against each other, some atoms in one of the objects may pull electrons away from atoms in the other object. The direction of electron transfer depends on the tendency of the materials to capture or give up electrons.
What is conduction?
Putting a charged object in contact with a neutral object.
What is induction?
Putting a charged object close to a neutral object without them touching.
What is an electroscope?
An electroscope is an instrument that is used to detect the presence and magnitude of the electric charge on a body.
What is dynamic electricity?
Dynamic electricity describes all the phenomena related to electrical charges in motion ( a moving current).
>Electrical circuits
What’s and electric current?
Electric current is the flow of negative charges (electrons).
What’s the current direction?
We use the conventional current (from positive terminal to negative terminal).
What is current intensity?
Current intensity is the number of charges that flow past a given point in an electrical circuit every second.
The symbol for current intensity is I (capital).
The units for current intensity is Amps (A).
What is potential difference (voltage)?
1) Potential Difference is the amount of energy transferred between two points in an electrical circuit.
The symbol for potential difference is V
The units for potential difference is Volts (V).
What is resistance?
Resistance us the ability of a material to slow down the movement of electric current.
The symbol for resistance is R.
The units for resistance is ohms ( sign)
Describe Ohm’s law:
Current intensity, potential difference and resistance are related to each other.
List the factors that affect conductivity:
1) Nature of the wire> made of copper
2) wire diameter> thicker wires are more conductive
3) wire length> shorter wires are more conductive
4) wire temperature> colder wires are more conductive
Explain conductance:
Conductance is the measure of how good a conductor is at carrying current.
A good conductor has a high conductance value and a very small resistance to current flow.
Conductance is the opposite of resistance. This is the measure of how easily electrons flow through a circuit.
Symbol: G
Unit: Siemens (S)
What is an electrical circuit and list the two types.
An electrical circuit is a network in which electrical charges can flow continuously in a loop.
1) Series circuit
2) Parallel circuit
Explain a series circuit:
A series circuit provides a single pathway for the current to flow.
All elements are connected end to end.
( If the circuit breaks, all devices using the circuit will fail.)
Explain Parallel Circuit:
A parallel circuity provides several pathways for the current to flow.
The circuit contains branches.
If the circuit breaks, some devices using the circuit will fail and others will work.
List Kirchoff’s laws for series circuits:
Current: I total= I1=12=13
Potential Diff: Vtot= V1+ V2+V3
Equivalent Resistance: Req= R1+R2+R3
List Kirchoff’s laws for parallel cicuits:
Current: Itot= I1+I2+I3
Potential Diff: Vtot= V1=V2+V3
Equivalent Resistance: 1/Req=1/R1 + 1/R2 + 1/R3
Define Energy and define the symbol and unit:
The ability to do work
Symbol:E
Unit: Joule (J)
Define Power and define the symbol and unit:
The amount of energy used in a given amount of time.
Symbol: P
Unit: Watt (W)
What does P=Edeltat mean?
P: power in watts
E: Energy in Joules
Delatt: Change in time in seconds
What is P=IV?
P= power in watts I= Current intensity in amps V= Voltage in volts
What does E=pt mean (calculating cost);
P= power in kilowatts t= time in hours E= energy in kilowatt hours
How do you go from watts to kilowatts
Divide by 1000
How do you go from kilowatts to watts
Multiply by 100
Explain resistors:
Resistors are often placed into a circuit to limit the flow of electrons.
What does the first and second band of a resistor represent?
The first and second bands give you the first two digits of the resistance.
What does the third band of a resistor represent?
The third band is the exponent on ten by which the first two digits must be multiplied.
What does the fourth band of a resistor represent?
The fourth band indicates the tolerance of the resistor ( +,- a%). This tells you how close the actual resistance will be to the value indicated by the bands.
List the types of energy:
Elastic, Electrical, Thermal, Radiation, Chemical, Wind, Sound, Hydraulic and Nuclear.
What is an energy transfer?
The movement of energy from one place to another.
What is energy transformation?
The changing of energy from one form to another.
What is the law of conservation fo energy?
Energy can neither be created nor destroyed; it can only be transferred or transformed. The total amount of energy in an isolated system always remains constant.
What is energy efficiency?
Rarely machines are able to convert all of one energy into another. Some energy is always lost to the surroundings. Our goal in creating machines is to make them as energy efficient as possible.
What’s the formula for energy efficiency?
Energy Efficiency= Amount of useful energy/ Amount of energy consumed (100)
What is temperature?
The measure of the agitation as well as the number of particles.
What is heat?
Depends on the degree of the agitation as well as the number of particles.
What is specific heat capacity?
The amount of thermal energy required to raise the temperature of one gram of a substance by one degree celsius. Each substance has a different specific heat capacity making it a characteristic property.
The symbol is “c”.
The unit is: Joule/ gram (degrees celsius) J/g *C
How do you measure temperature?
Using a thermometer
How do you measure heat?
Using a thermometer and an equation. (Q=mcdeltaT)
What does Q represent in Q=mcdelatT
Thermal energy
Unit: Joule
Unit Symbol: J
What does M represent in Q=mcdelatT
Mass
Unit: Gram
Unit symbol: g
What does DeltaT represent in Q=mcdelatT?
Change in temperature
Unit: Degrees celsius
Unit Symbol: *C
What does C represent in Q=mcdelatT?
Thermal energy
The symbol is “c”.
The unit is: Joule/ gram (degrees celsius) J/g *C
