Knowt
ch 22 sec 1_Current_and_Circuits w 8 tr 2
Page 1: Introduction to Electric Current
Electric current is defined as the flow of electric charges.
KWL Chart:
K: What I Know
W: What I Want to Find Out
L: What I Learned
Page 2: Essential Questions
What is electric current?
How does energy change in electric circuits?
What is Ohm’s law?
How are power, current, potential difference, and resistance mathematically related?
Page 3: Review Vocabulary
Important terms:
Electric potential difference
Electric current
Conventional current
Battery
Electric circuit
Ampere
Resistance
Resistor
Parallel connection
Series connection
Page 4: Producing Electric Current
Charges flow between conductors with different electric potentials until equilibrium is reached.
Electric current refers to the flow of charged particles.
Conventional current is the direction a positive test charge moves, opposite to the flow of electrons.
Page 5: Maintaining Electric Current
To maintain potential difference, charged particles can be pumped back to higher potential areas.
This process requires an external energy source.
Voltaic or Galvanic cell: Converts chemical energy to electric energy.
Photovoltaic cell: Converts light energy to electric energy.
Page 6: Electric Circuits
Electric Circuit: A closed loop that allows electric charges to flow.
Includes a charge pump to increase potential energy and a device to reduce potential energy.
Page 7: Charge and Energy Conservation
Charge is conserved; it cannot be created or destroyed.
The total charge remains constant in a circuit.
Energy is also conserved where the change in electric energy equals the potential energy lost.
Page 8: Rates of Charge Flow
Electric current ( I ) is the rate of charge flow represented by the equation I = q/t (where q is charge and t is time).
SI Unit for Electric Current: Ampere (A) - equivalent to one coulomb per second.
Energy carried by current: E = qΔV
Power calculation: P = E/t, substituting E = qΔV and q = It.
Page 9: Solving Power Problems
Power unit: Watts.
Energy unit: Joules.
Example Problem: For a 120-V motor at 13 A, determine power and energy used over one hour.
Known Values:
∆V = 120 V
I = 13 A
t = 3600 s
Page 10: Circuit Diagrams
Circuits can be described in various ways:
Written description
Photographic representation
Circuit diagrams (schematics)
Page 11: Common Circuit Symbols
Familiarize with common electronic circuit symbols for components (e.g., resistors, batteries, etc.).
Page 12: Resistance and Ohm’s Law
Resistance is the property determining current flow in a circuit.
Measured by voltage/current (R = ΔV/I).
SI Unit: Ohms (Ω).
1 Ω allows 1 A flow with a 1 V potential difference.
Current changes can be achieved by varying voltage (V) or resistance (R).
Page 13: Ohm’s Law and Circuit Components
Components with constant resistance follow Ohm’s law.
Most metallic conductors obey Ohm's law within specified limits.
Electronic components like transistors and diodes do not obey Ohm's law.
Resistors provide specific resistance; variable resistors (potentiometers) control current.
Page 14: Evaluating Current Example
Example: Determining current flow in a circuit with a 9.0-V battery and a 15-kΩ resistor.
Known Values:
∆V = 9.0 V
R = 15 kΩ
I = ?
Page 15: Parallel and Series Connections
Parallel Connection: Exists when a voltmeter is connected across components; multiple paths for current.
Potential difference across components equals the voltmeter's reading.
Page 16: Series Connection
Series Connection: There is only one path for current, as measured by an ammeter.
Current through components aligns; this is associated with terms like "current through" in circuits.
Page 17: Vocabulary Summary
Review essential questions and terms:
Electric current, conventional current, battery, electric circuit, ampere, resistance, resistor, parallel connection, and series connection.
