Electrical Circuits: Voltage, Current, Resistance

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Questions and Answers

What is the difference between Static Electricity and Current Electricity?

Static electricity is the buildup of electric charges on a surface. Current electricity is the flow of electric charge through a conductor.

__________ means there are equal numbers of electrons and protons in an object. A __________ is when you have an excess of electrons, and a __________ charge is when you have a lack of electrons.

Neutral charge, negative charge, positive

What are the “3 Laws of Electric Charges”?

  1. Opposite charges attract each other. 2. Like charges repel each other. 3. Charged objects can attract neutral objects.

You have two strips of acetate (plastic) and some rabbit's fur. If you rub one with rabbit's fur and don't do anything to the other, how will the strips respond to one another? What if you rub both with fur, how will they respond to one another then? Explain.

<p>If you rub one strip with rabbit's fur, it will become negatively charged. The unrubbed strip will remain neutral. They will attract each other. If you rub both strips with fur, they will both become negatively charged and repel each other.</p> Signup and view all the answers

What does it mean if you “Ground” an object?

<p>To &quot;ground&quot; an object means to connect it to the Earth, allowing electric charge to flow between the object and the Earth. This neutralizes the object.</p> Signup and view all the answers

What is the difference between an Open Circuit and a Closed Circuit?

<p>An open circuit has a break in the path, preventing current flow. A closed circuit has a complete path, allowing current to flow.</p> Signup and view all the answers

Describe the parts of an electric circuit and give an example of each.

<p>Source: provides energy (e.g., battery). Conductor: allows current flow (e.g., wire). Load: uses the energy (e.g., light bulb).</p> Signup and view all the answers

Draw the following circuit symbols: a) cell b) battery c) lamp d) switch e) resistor f) variable resistor (rheostat) g) ammeter h) voltmeter

<p>a) Cell: | - b) Battery: | |- | - c) Lamp: circle with a X inside d) Switch: --/ o e) Resistor: zigzag line f) Variable resistor: zigzag line with arrow through it g) Ammeter: circle with A inside h) Voltmeter: circle with V inside</p> Signup and view all the answers

A __________ circuit is one in which there is only one pathway for the electricity to move through. Once the circuit is broken, it fails to work. On the other hand __________ circuits have multiple pathways in which the electricity can travel though.

<p>series, parallel</p> Signup and view all the answers

Draw a circuit with two lamps, a motor and two switches. One switch should control one lamp and the motor at the same time and the second switch should control only the other lamp.

<p>Circuit should include a power source, two lamps, a motor, two switches, and connecting wires. One switch connected in series with one lamp and the motor, and the other switch connected in series with the other lamp.</p> Signup and view all the answers

Explain the differences between CURRENT and VOLTAGE.

<p>Current (a.k.a. amperage): rate of electrical flow, measured in amps, must be inserted in the circuit. Voltage: electrical potential difference, measured in volts, must be inserted parallel to the circuit.</p> Signup and view all the answers

Resistance is __________. The unit used to measure this is called __________ and it's symbol is __________.

<p>the opposition to current flow, Ohms, Ω</p> Signup and view all the answers

Calculate the following. Show the formulas and all your work. (Remember the triangle!) a) What is the resistance of a wire if the voltage going through the wire is 110V and the current is 50 Amps. b) What is the current going through the device if the resistance is 120 Ω and the potential difference is 50A

<p>a) R = V/I = 110V / 50A = 2.2 Ohms. b) I = V/R = 50A / 120 Ω = 0.417 Amps</p> Signup and view all the answers

What are the four things that would affect electrical resistance? List them and explain how resistance is affected.

<p>Length: longer increases resistance. Thickness: thicker decreases resistance. Temperature: higher increases resistance. Material: different materials have different resistance.</p> Signup and view all the answers

These devices convert energy forms. Describe how each works including the energy it uses and the energy that is produced. Thermocouple (thermo-electric generator) Piezoelectric Effect Photovoltaic Cells LED

<p>Thermocouple: Converts thermal energy to electrical energy. Piezoelectric Effect: Converts mechanical stress to electrical energy. Photovoltaic Cells: Converts light energy to electrical energy. LED: Converts electrical energy to light energy.</p> Signup and view all the answers

__________ cell is a device that creates electricity from two different electrodes and an electrolyte.

<p>Voltaic</p> Signup and view all the answers

Compare and contrast the following terms: Anode Cathode Primary Cell Secondary Cell Dry Cell Wet Cell

<p>Anode: positive electrode/ Cathode: negative electrode. Primary Cell: non-rechargeable/ Secondary Cell: rechargeable. Dry Cell: uses paste electrolyte/ Wet Cell: uses liquid electrolyte.</p> Signup and view all the answers

What is the difference between a GENERATOR and a MOTOR?

<p>Generator: converts mechanical energy into electrical energy. Motor: converts electrical energy into mechanical energy.</p> Signup and view all the answers

One type of current is called __________ because it changes direction as it moves though the wire. This is most commonly used in our homes because the voltage is easy to increase to travel long distances. The other type of current is called __________ and is called this because the current only moves in one direction. A generator that produces this type of current is called a __________.

<p>alternating current (AC), direct current (DC), commutator</p> Signup and view all the answers

What does each of the following parts on a St. Louis motor do? (p. 315)

<p>Posts: provide support. Brushes: make electrical contact. Split Ring Commutator: reverses current direction. Armature (Electro-magnet): rotates when energized. Permanent (field) magnets: create magnetic field.</p> Signup and view all the answers

How does power get to your house? What devices does it have to pass through?

<p>Power is transmitted through power lines from generating stations to substations, then to transformers, and finally to your house through distribution lines and a meter.</p> Signup and view all the answers

What is a Transformer? (Step-Up/Step-Down)

<p>A transformer is a device that increases or decreases voltage levels in an AC circuit. A step-up transformer increases voltage, while a step-down transformer decreases voltage.</p> Signup and view all the answers

Describe the purpose of fuses and circuit breakers then explain the difference between them.

<p>Purpose of both devices: to protect circuits from overcurrent. Fuses: melt and break the circuit when overcurrent occurs, must be replaced. Circuit Breaker: trips and opens the circuit when overcurrent occurs; can be reset.</p> Signup and view all the answers

A current of 22.6 amps passes through an electric heater when it is connected to a 120 volt wall outlet. What is the power of the heater? (Show the formula and all work.)

<p>P = V * I = 120V * 22.6A = 2712 Watts</p> Signup and view all the answers

A television uses 230 W of power. The T.V. is used for 160 hours per month. Power costs $0.09 per kilowatt hour. Calculate the cost of using the T.V. for three months. (Show your work.)

<p>Energy used per month = 230W * 160 hours = 36800 Wh = 36.8 kWh. Cost per month = 36.8 kWh * $0.09/kWh = $3.312. Cost for three months = $3.312 * 3 = $9.94</p> Signup and view all the answers

What are different methods of ELECTRICAL PRODUCTION? What are their draw backs and advantages?

<p>Fossil fuels: Drawback is they produce pollution. Renewable energy(solar, wind, hydro): Drawback is they are intermittent. Nuclear: Drawback is they generate nuclear waste.</p> Signup and view all the answers

Flashcards

Static Electricity

Charges stay in one area; caused by imbalance

Current Electricity

Flow of electrical charge (i.e., electrons) through a conductor.

Neutral Charge

The object has equal numbers of electrons and protons.

Negative Charge

Object has an excess of electrons.

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Positive Charge

It has a lack of electrons.

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Laws of Electric Charges

Like charges repel, opposite charges attract, charged objects attract neutral objects.

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Grounding

Creating a direct pathway to the Earth, neutralizing it.

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Open Circuit

A circuit with a break, stopping current flow.

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Closed Circuit

A complete, unbroken path for current flow.

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Source in a circuit

Provides voltage for the circuit, battery.

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Study Notes

  • Voltage, current, and resistance are compared in circuits.
  • Devices used to convert electrical energy are described.
  • The power and efficiency of various devices are examined.

Static vs. Current Electricity

  • Equal numbers of electrons and protons are present in an object, then it's neutral
  • An excess of electrons is a negative charge.
  • A lack of electrons is a positive charge.

Laws of Electric Charges

  • First Law
  • Second Law
  • Third Law

Grounding an Object

  • Grounding refers to connecting an object to the Earth to neutralize electrical charge.

Open vs. Closed Circuit

  • Open Circuit
  • Closed Circuit

Electric Circuit Parts

  • Source: Provides the energy (e.g., battery).
  • Conductor: Allows electron flow (e.g., wire).
  • Load: Uses the electrical energy (e.g., light bulb).
  • Control: Manages the circuit (e.g., switch)

Circuit Symbols

  • Cell
  • Battery
  • Lamp
  • Switch
  • Resistor
  • Variable Resistor (Rheostat)
  • Ammeter
  • Voltmeter

Types of Circuits

  • A series circuit has only one pathway for electricity; if broken, it fails.
  • Parallel circuits have multiple pathways for electricity.

Current vs. Voltage

  • Current
    • Definition
    • Abbreviation
    • Device used to measure
    • How does it need to be inserted into the circuit
  • Voltage
    • Definition
    • Abbreviation
    • Device used to measure
    • How does it need to be inserted into the circuit

Resistance

  • Resistance opposes the flow of electric current.
  • The unit to measure resistance is called an Ohm, and its symbol is Ω.

Factors Affecting Electrical Resistance

  • Length: resistance increases with length.
  • Thickness: resistance decreases with thickness.
  • Temperature: resistance usually increases with temperature.
  • Material of the conductor.

Energy Conversion Devices

  • Thermocouple
  • Piezoelectric Effect
  • Photovoltaic Cells
  • LED

Electrochemical Cell

  • Electrochemical cell is a device that creates electricity from two different electrodes and an electrolyte.

Electrochemical Cells

  • Anode vs Cathode
  • Primary Cell vs Secondary Cell
  • Dry Cell vs Wet Cell

Generator vs. Motor

  • Generator
  • Motor

Types of Current

  • Alternating Current (AC) changes direction and is used in homes because voltage is easy to increase for long distances.
  • Direct Current (DC) moves only in one direction.
  • A generator that produces DC is called a dynamo.

St. Louis Motor

Electrical components

  • Posts
  • Brushes
  • Split Ring Commutator
  • Armature (Electro-magnet)
  • Permanent (field) magnets

Delivering Power

  • Power gets to your house through a series of devices.

Transformer

  • A Transformer changes (steps up or steps down) voltages

Fuses and Circuit Breakers

  • Purpose of both devices: Safety
  • Differences Between the Devices
    • Fuses
    • Circuit Breakers

Electrical Production

  • Different methods of ELECTRICAL PRODUCTION, their draw backs and advantages

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