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 ...