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Chapter 7
Section 2
What Is Electric Current?
- net movement of electric charges
(electrons) in a single direction
- measured in amperes
This diagram shows a simple LED driver circuit. When the
battery is connected the positive end of the battery pulls
electrons from the negative end of the battery and through
the circuit. This circuit has three basic properties: voltage,
current, and resistance.
What Is a Voltage (Potential) Difference?
- the force that causes
electrons to flow
- electric charge flows from
a higher voltage to a lower
voltage
Circuit = a closed path that electric
current follows
This flow of electrons can power things
like light bulbs
Batteries
• Dry cell battery is the most common type of battery. It is called
a dry cell because the electrolyte is a moist paste and not a
liquid solution.
• Wet cell battery is a battery that contains a series of wet liquid
solution cells connected together.
• Lead-acid battery is the type used in cars. It is like the wet cell
battery in that is a series of cells connected together immersed in
a liquid. The liquid in this specific type of battery is a sulfuric acid
solution and the plates in the battery are made specifically of
lead.
Resistance = tendency for material to
oppose the flow of electrons
-- electric current loses energy as it flows
-- resistance is measured in OHMS
* Copper has a low
resistance, hence it is
used for household
wiring and other
electronics
STOP AND THINK
1. A positively charged subatomic particle is ____
negatively charged subatomic particle is ____
2. Amperes are used to measure _________
3. A closed path that electrons (current) can flow through is a:
4. Materials that current can flow through easily are called:
5. OHMS are used to measure the __________ of a circuit.
As the length of a
wire increases, so
does its resistance
As the wire becomes
thinner, its resistance
increases
the thin wire in a
tungsten light bulb glows
due to this resistance
Ohm's Law -- the current (I) in a circuit
equals the voltage difference (V)
divided by resistance (R)
Quick Calculations:
1. What is the current of a circuit with a
voltage difference of 20 volts and a
resistance of 10 ohms.
2. What is the Voltage difference in a circuit
with a resistance of 11 ohms, and a current
of 2 amperes.
1. What is the center of an atom called?
2. Electrons are attracted to _________
3. Electrons move from the ___ to the ___ side of a battery.
4. What is the most common metal used in wiring?
5. How many volts are in an AA battery? ______
6. How many volts are in a wall outlet?
7. A device used to turn electricity on and off is a _______
8. In which type of circuit can you turn a light off and the other
will stay on? [ series / parallel ]