Download Physical Science Chapter 6 Notes Section 1: Electric Charge 1. An

Physical Science
Chapter 6 Notes
Section 1: Electric Charge
1. An atom naturally has no electrical charge; that is, it is electrically neutral. When an atom gains or
loses an electron it then acquires a charge and is ionized.
♦ To be electrically neutral an atom must have the same number of protons and electrons
• A proton has a positive charge
• An electron has a negative charge
♦ An electric charge can be transferred from object to another
♦ In an atom the electron (which has a negative charge) is the only particle that can move
♦ When an atom gains an electron it becomes negatively charged because the electron carries a
negative charge
♦ When an atom loses an electron it becomes positively charged for the same reason
♦ Atoms with like charges repel each other, and atoms with opposite charges attract each other
2. Electric field – a region surrounding every electric charge in which a force of attraction or repulsion is
exerted on other electric charges
3. Static electricity – the buildup of an electric charge on an object
4. Law of Conservation of Charge – an electric charge cannot be created or destroyed. The charge, in
the form of an electron can be moved from one place to another.
5. Electric Discharge – the transfer of an electric charge. When two oppositely charged objects come
in contact, electrons will move until both objects are electrically neutral.
Section 2: Electric Current
1. Electric Current – the net movement of electric charges in a single direction.
♦ In an electric circuit the electrons flow from the negative pole to the positive pole.
♦ Current is measured in amperes (amps)
♦ There are two types of currents: direct current and alternating current
• Direct current (DC) – the electrons flow in only one direction
• Alternating current (AC) – the electrons repeatedly change direction in their flow
2. Electric cell – converts chemical energy into electric energy
♦ Contains two terminals (positive and negative) of different kinds of metals
♦ Also contains an electrolyte. An electrolyte is a substance that allows an electric current to be
conducted
♦ There are two types of cells: dry and wet
• Dry cell – the electrolyte is a paste
• Wet cell – the electrolyte is a liquid
♦ Battery – a collection of two or more electric cells
3. Coulomb’s Law – used to determine the charge and voltage on a capacitor
C=
Q
V
C = capacitance
Q = charge
V = voltage
Q
C
V
4. Electrical Potential Energy – the electrons stored energy. Better known as voltage.
♦ Potential Difference – is the difference in the number of electrons on the negative pole of a cell
when compared to the lack of electrons on the positive pole of the cell?
♦ Ohm’s Law – used to measure voltage, resistance, and current in a circuit
V = IR
♦
V = voltage
I = current
R = resistance
V
I
R
Power – the rate at which energy is delivered. Power is measured in watts
2
P = IV
P = I 2R
P=
V
R
Section 3: Electric Circuits
1. Electric circuit – the path electricity follows. There are two types of circuits, series and parallel
♦ Series circuit – only has one path for the electricity to follow. The current flows from the negative
pole to the positive pole.
+
♦
Parallel circuit – has two or more separate paths through which electricity can flow. The current
flows from the negative pole to the positive pole.
+
2. Conductor – a material through which electricity can flow
3. Insulator – a material that will not carry current
4. Resistance – a measure of how much a substance opposes the flow of electricity
♦ Resistance in a circuit causes electrical energy to convert to heat energy
♦ Different materials provide different levels of resistance
♦ Resistance is measured in ohms (symbol is Ω)
5. Capacitor – consists of two metal plates separated by an insulator. Electric charge will build up on
one plate until enough charge has accumulated to “jump” the gap between the plates.
6. Open circuit – a circuit in which the switch is off or there is a break in the circuit.
7. Closed circuit – a circuit in which the switch is on or there are no breaks in the circuit