Key-Circuit-Electricity-Study-guide-Review

Chapter 6: Electricity Study Guide

1. Electric Current

  • Definition: Flow of electric charge.

  • Unit: Ampere (A) or Amps.

    • 1 A = 1 coulomb per second.

  • Current Flow:

    • Defined as the flow of positive charges, despite electrons flowing in the opposite direction.

    • Electron Flow: Actual flow of electrons (opposite of current direction).

  • Types of Current:

    • Direct Current (DC): Flows in one direction (e.g., battery-operated devices).

    • Alternating Current (AC): Changes direction (e.g., electricity in homes and schools).

2. Conductors and Insulators

Conductors

  • Definition: Materials through which charge can flow easily.

  • Characteristics:

    • Usually metals (e.g., copper, silver).

    • Possess free electrons that move easily.

Insulators

  • Definition: Materials through which charge cannot flow easily.

  • Examples: Wood, plastic, rubber, dry air.

  • Characteristics:

    • Bound electrons that do not move easily.

3. Resistance

  • Definition: Opposition to the flow of charges in a material.

  • Measurement: Measured in Ohms (Ω).

  • Factors Affecting Resistance:

    • Thickness: Thicker materials have lower resistance.

    • Length: Shorter materials have lower resistance.

    • Temperature: Lower temperatures generally mean lower resistance (superconductors).

  • Resistors: Objects with resistance that convert electrical potential energy into other forms of energy (e.g., light or heat from a light bulb).

4. Voltage

  • Definition: Difference in electric potential between two locations in a circuit or electric field.

  • Measurement: Measured in Volts (V).

    • Electric potential energy per charge.

    • Sometimes referred to as potential difference.

    • 1 V = 1 Joule per coulomb.

  • Voltage Flow: Current flows naturally from high voltage to low voltage. Voltage decreases as charge flows through the circuit, being converted to other forms of energy.

5. Voltage Sources

  • Function: Increase electric potential energy of electric charges.

  • Examples:

    • Batteries: Convert chemical energy to electrical energy.

    • Solar Cells: Convert sunlight to electrical energy.

    • Generators: Convert mechanical energy to electrical energy.

6. Ohm's Law

  • Formula: V = IR, where V = Voltage, I = Current, R = Resistance.

  • Manipulations:

    • I = V/R (current = voltage/resistance).

    • R = V/I (resistance = voltage/current).

7. Electrical Safety

  • Safety Devices:

    • Fuses, circuit breakers, Ground Fault Circuit Interrupter (GFCI).

    • Grounding: Grounding prong in plugs.

  • Personal Safety Practices:

    • Avoid touching exposed wires.

    • Do not interact with electrical devices using wet hands.


More Complex Circuits

1. Circuit Basics

  • An electric circuit must have a source of electrical energy and devices run by that energy.

2. Circuit Types

Series Circuits

  • If one element fails, the whole circuit stops working.

  • Voltage adds up across each device ( V_total = V_1 + V_2 + V_3 + ...).

  • Resistance adds as well ( R_total = R_1 + R_2 + R_3 + ...).

Parallel Circuits

  • If one element fails, others can still operate.

  • Voltage remains the same across all devices ( V_total = V_1 = V_2 = V_3 ...).

  • Current divides among the branches.

3. Electrical Power and Energy

  • Power: Calculated as voltage multiplied by current (P = VI).

  • Electrical Energy: Given by the equation E = Pt (energy = power x time).

  • Formulas:

    • Watts = Volts x Amperes.

    • Joules = Watts x Seconds.

Cost of Electrical Energy

  • Average cost calculated using the formula: Cost = (Energy used in kWh) x (Cost per unit in $/kWh).


Circuit Rules (For the Test)

Series Circuits

  • Voltage: Adds up across components; V_total = V_1 + V_2 + V_3 ...

  • Current: Same through all components; I_total = I_1 = I_2 = ...

  • Resistance: Adds up; R_total = R_1 + R_2 + R_3 ...

Parallel Circuits

  • Voltage: Same across all branches (V_total = V_1 = V_2 = ...).

  • Current: Splits across branches; I_total = I_1 + I_2 + I_3 ...

  • Resistance: Calculated using the reciprocal formula: 1/R_total = 1/R_1 + 1/R_2 + 1/R_3 ...

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