Electricity 2

objectives

• Bill Nye video “Electricity”

• Crossword

Electric Potential Energy

• Stored electrical energy

Ex. A battery has stored electrical energy because the electrons have the ability to do work after they leave the battery.

Electric Potential Difference

• The change in potential energy per coulomb of charge.

• Also called voltage

• Measured in volts (V)

• Measured using a voltmeter

Electric Charge

• A building up at the negative terminal of a cell/battery which then flows from this terminal as negative charges repel one another.

Electrochemical cell & Electric Charge

• Two types of electrochemical cells – dry cells (battery in a flashlight) and wet cells (battery in a car)

• Both types produce voltage

Electrochemical Cell

• An electrochemical cell is a device or a mechanism that can either generate electrical energy from a chemical reaction or utilize electrical energy to produce a chemical reaction.

Electrochemical cell

Electrochemical cell is made of;

• 2 electrodes usually made of different metals

• The electrodes are in an electrolyte, which is a substance that conducts electricity

• Dry cell – electrolyte is a paste

• Wet cell – electrolyte is a fluid

How it Works

• The acidic electrolyte attacks the zinc electrode and pulls atoms off the zinc.

• But the zinc atoms leave electrons behind on the electrode, and the electrode becomes negatively charged

• At the same time, chemical reactions pull electrons off the copper electrode

• Therefore the copper electrode has a positive charge. Because there is an opposite charge on each electrode, there is a potential difference (voltage) between the two electrodes.

Electric Circuit

• A complete pathway that allows electrons to flow.

• Will transform electrical energy into other forms of energy.

Parts of an Electric Circuit

Describe the parts of an electric circuit;

• Source of electrical energy

• Electrical load

• Control / switch

• conductor

Electric Current

• The amount of charge passing a given point in a conductor per second.

• Measured in amperes (A)

• Measured using an ammeter

Flow of Electric Current

Current Electricity

• The continuous flow of charge in a complete circuit.

Circuit Diagrams

Circuit Diagram Symbols: Page 262

• Bulb

• Cell

• Battery

• Wires

• Resistors

• Ammeter

• Voltmeter

• Open / closed switch

How to Draw a Circuit Diagram

Worksheets

• Drawing circuit diagrams

• How to make light bulbs glow

• Potential energy is stored energy

• In a circuit, the battery stores energy (source of the potential energy). Once it is connected to a light bulb, the electric potential energy is “released”. As the electrons move through the wire inside the bulb, the electrons energy is converted to heat and light energy.

Electrical Resistance

• Slows down the flow of electrons and converts electrical energy into other forms of energy.

• Measured in ohm’s (Ω)

• The ratio of the voltage to the current.

Factors affecting resistance in a wire

• Length

• Diameter

• Type

• temperature

Resistors

• Used to control current or potential difference in a circuit.

Textbook Page 277

• Resisters Values Worksheet

Ohm’s Law

• The mathematical relationship comparing voltage (V), current (I) and resistance (R)

V

I R

Calculate Voltage, Current, & Resistance

Practice Problems Page 273-274

Worksheets – calculating voltage, current, and resistance.

Lab Page 278-279