Download Electricity-and-Magnetism

ELECTRICITY and MAGNETISM
Key Terms
1. Circuit: uninterrupted path between the terminals of a power source.
2. Current: the amount of charge that passes a given point in a specified period of time, measured in
amperes(amps, A); flow of electrons through a circuit.
3. Closed Circuit- direction of current flow from positive to negative terminal when powered by a battery
4. Schematic- special type of diagram used by physicists and electricians to represent a circuit.
5. Electric potential: the potential energy per unit of positive charge; measured in volts.
6. Voltage- the difference between these two potentials in a battery; measured in volts.
7. Resistance- the decrease in the flow of electrons and current due to a change in the diameter or material of a
wire; measured in ohms ( O ).
8. Ohm’s Law- the ratio of voltage to current is resistance and is represented by the equation R=V/I, where R=
resistance, V= voltage, and I= current.
9. Potential difference- the difference in electric potential between point A and point B. I a circuit, point A and
point B represent the positive and negative terminals of a power source such as a battery.
10. Resistor- any wire in a circuit which causes a decrease in the flow of current due to its diameter or material;
e.g. filament in a light bulb.
11. Tesla (T) – Unit of measure for the magnitude of a magnetic field.
12. Magnetism – property of matter; some metals e.g. iron can be permanently magnetized.
13. Electromagnet-metal magnetized with electric current flowing through it
Investigation One
A) Direct relationship between voltage and current as one changes the other changes in same manner
1) voltage and current increase as the number of batteries increases; direct relationship between voltage and
current
2) the change in current in a circuit is inversely proportional (opposite) to the resistance; as resistance in a
circuit increases, the current decreases e.g. current increased as voltage increased but the circuit with the greater
resistance had lower current than the circuit with the lesser resistance
3) relationship among voltage, current and resistance is described by Ohm’s law V=IR
Investigation Two
A) As resistance increases by changing the resistor the current decreased
1) resistance provided by 2 resistor in series is approximately twice the resistance provided by single resistor
2) resistance provided with 2 resistors in parallel approximately one-half the resistance of single resistor
3) change length of resistor changes resistance; increasing length, increases resistance or decreasing length,
decreases resistance
4) changing cross-sectional area of resistor changes resistance; increasing cross-sectional area decreases the
resistance or decreasing cross-sectional area increases the resistance
B) Resistance is ratio between the voltage and current in a circuit; as voltage changes, current changes in
proportion to the voltage but resistance remains constant
1) voltage held constant, current changes only if amount of resistance in circuit changes
2) increasing resistance by changing resistors results in decrease in current proportional to change in resistance
but voltage remains constant
3) Ohm’s law also applies regardless of whether multiple resistor are placed in series or in parallel
Investigation Three
A) Magnetism- property of matter
1) temporary magnets- wrapping coil of wire around a piece of metal and passing electric current through wire
2) electromagnet- stays magnetic as long as electric current is flowing
3) Electromagnet- magnetic strength increases as the current increases
B) Magnetic field – the strength of this make is determined by the size of magnetic field; in units of Tesla (T)
1) current is directly related to the strength of the magnetic field; increasing # batteries increases strength of
magnetic field by increasing the current or decreasing current cause a decrease in the magnetic field
2) magnetic field increases when current, number of turns of wire or length of coil increases
C) Direct relationship between electricity and magnetism; amount of current flowing through the wire increases
the magnitude of magnetic field increases
D) Strength of electromagnet
1) affected by the number of turns of wire in a coil over a specific length; # of turns of wire increases strength
2) affected by the amount of current flowing through the wire; increasing amount of current increases strength