7-2 Electric Current Notes
What is an Electric Current?
The ______through a wire of conductor is called ______
Current is usually the flow of ______
Electric current is measured in ______(___)
Charges flow from ______voltage to ______voltage (______
______-must be present)
A voltage difference is the ______that causes charges to move.
Voltage difference is measured in ______.
For charges to flow, the wire must always be connected in a ______
______
If the circuit is broken by removing the battery, or the lightbulb, or one of the wires, current will ______.
Batteries
To keep an electric current continually flowing in the electric circuit a voltage difference needs to be maintained in the circuit.
A battery can provide the voltage difference that is needed to keep current flowing in a circuit.
______as long as there is a ______that connects one battery terminal to the other battery terminal.
Dry-Cell Batteries
A cell consists of ______surrounded by a material called an______.
The electrolyte enables charges to move from one electrode to the other.
One electrode is the carbon rod, and the other is the zinc container.
The electrolyte is a ______containing several chemicals.
The cell is called a dry cell because the electrolyte is a moist paste, and not a liquid solution.
Sources of Electricity
A ______produces a voltage difference between its ______container and its ______suspension rod, causing current to flow between them
Sources of Electricity
A ______contains two connected plates made of different ______in a conducting ______
A wet-cell battery contains several wet cells connected together.
Sources of Electricity
______have a voltage difference across the ______of an electrical outlet, and a generator at a ______provides this voltage difference
What is Resistance?
______
______the ______of electrons
electrical energy is converted to ______&______
all materials have ______electrical resistance
Resistance is measured in ______(____)
Making wires ______, or hotter ______the resistance
Ohm’s Law
Ohm’s Law – the current in a circuit equals the voltage difference divided by the resistance
V: potential difference (V)
I: current (A)
R: resistance ()
- Voltage ______when ______increases.
- Voltage ______when ______increases.
Ohm’s Law Problem
- A lightbulb with a resistance of 160 is plugged into a 120-V outlet. What is the current flowing through the bulb?
Question 1
______is the net movement of electric charges in a single direction.
A. An open circuit
B. Electric current
C. Proton flow
D. Voltage
Question 2
What is a volt?
Answer
Question 3
What is the tendency for a material to oppose the flow of electrons called?
Answer
What property of electric current causes light bulbs to give light?
Notes 7-3 Electrical Circuits
Electrical Circuits
Circuits rely on generators at power plants to produce a ______across the outlet, causing the charge to move when the ______
Example
Hair dryer plugged into wall outlet
Generator at power plant produces voltage difference
Dryer and circuit in house contain conducting wires to carry current
Hair dryer turns electrical energy into thermal energy and mechanical energy
Unplug hair dryer opens circuit and breaks path of current
The Current in a Simple Circuit
A simpleelectric circuit contains a source of ______, such as a battery, a device, such as a lightbulb, that has ______, and ______that connect the device to the battery terminals.
When the wires are connected to the battery terminals, ______in the ______.
Circuit Components
A - batteryC - light bulb
B - switchD - resistor
Types of Circuits
______circuit – the current has only ______to flow through
______circuit – are used in ______
Series Circuit
current travels in a ______path
–______- one ______the flow of current
current is the ______throughout circuit
–lights are ______brightness
each device receives a ______of the total voltage
–gets ______as lights are added
______– if any part of a series circuit is disconnected, ______through the circuit
Example: ______
Parallel Circuit
Parallel circuit – contains ______for current to move through.
The current can flow through both or either of the branches.
Example: ______
Advantage
When one branch of the circuit is opened, such as when you
turn a light off, the current continues to flow through the
other branches.
Household Circuits
Household circuits mainly use ______circuits connected
in a logical network.
Electrical energy enters your home at the ______or ______and branches out to wall sockets, major appliances, and lights.
Guards against overheating electric wires:
______– contains a small piece of metal that melts if the current becomes too high, opening the circuit and stopping the flow of current.
To enable current to flow again in the circuit, you must ______the blown fuse with a new one.
Too many appliances in use at the ______is the most likely cause for the overheating of the circuit.
Household Fuse Box
Guards against overheating electric wires:
______– contains a small piece of metal that bends when it gets hot, opening the circuit and stopping the flow of current.
Circuit breakers usually can be reset by pushing the switch to its “on” position.
Breaker Box
Electrical Power
Electrical energy is easily converted to mechanical, thermal, or light energy.
Electrical power – the ______
______
Electrical Power - rate at which electrical energy is ______to another form of energy P: ______(____)
I: ______(____)
V: ______(__)
Electrical Poweris expressed in ______
The unit for power is the watt (W). Because the watt is a small unit of power, electric power is often expressed in ______
One kilowatt equals ______.
P (watts) = I (amperes) x V (volts)
To calculate the amount of energy an appliance uses:
The unit of electrical energy is the kilowatt-hour, which equals 1000 watts of power used for one hour.
Energy = power x time
E (kWh) = P (kW) x t (h)
Electrical Power
A calculator has a 0.01-A current flowing through it. It operates with a potential difference of 9 V. How much power does it use?
Electrical Energy
Electric companies charge by the amount of electrical energy used, rather than by the electric power used.
Electrical energy usually is measured in units of kilowatt hours (kWh) and can be calculated from this equation:
Electrical Energy
–energy use of an appliance depends on power required and time used
E: ______(______)
P: ______(______)
t: ______(_____)
The Cost of Using Electrical Energy
•The cost of using some household appliances is given in this table, where the cost per kWh is assumed to be $0.09/kWh.
Electrical Energy
A refrigerator is a major user of electrical power. If it uses 700 W and runs 10 hours each day, how much energy (in kWh) is used in one day?
Question 1
What is an open circuit?
Answer
Question 2
The rate at which electrical energy is converted to another form of energy is called ______.
A. electrical fuse
B. electrical switching
C. electric power
D. thermal energy
Question 3
Which of the following equations is used to calculate electric power?
A. P = IV
B. P = I/V
C. P = V/I
D. P = AV
Why do homes have a fuse box or circuit breaker?
How does it work?