# Ch. 8: Ohm’s Law Current, Voltage & Resistance. Electric potential Energy increases when unlike charges move further apart Electric potential difference.

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Ch. 8: Ohm’s Law Current, Voltage & Resistance

Electric potential Energy increases when unlike charges move further apart Electric potential difference (voltage) is the change in electric potential energy per coulomb of charge Voltage is measured in volts (V) Electrical energy depends on the amount of charge and voltage Electrochemical cells (batteries) are a common source of voltage Voltmeters measure potential difference (voltage) 8.1 Electric Potential Energy & Voltage

Battery An electrochemical cell Electrochemical cell Converts stored chemical energy into electrical energy

Battery Terminals Battery Terminals Positive or Negative End points where a connection can be made Electrochemical cells/Batteries have separate positive and negative charges the negative terminal has excess electrons the positive terminal has less electrons

Typical household battery (C, D, AA & AAA) potential difference of 1.5 Volts (V) Wall sockets potential difference of 120 to 230 Volts (V)

Voltaic Pile Invented the first battery in 1799 Alessandro Volta The Volt (V) was named in his honour

Kinetic & Potential Energy Energy The ability to do work Kinetic Energy Energy a moving object has because of its motion Potential Energy energy stored in an object

Electric Potential Energy Potential Energy: energy stored in an object Electric Potential Energy: Electrical energy stored in a battery

Potential Energy & Potential Difference The potential energy in a battery is due to … 1. The amount of charge that has been separated (coulombs) 2. The potential difference/voltage (volts)

Electrochemical cells (batteries) separate positive & negative charges The greater the difference, the greater the amount of charge (Coulombs) in this battery 1. The amount of Charge that has been separated (Coulombs) The potential energy in a battery is due to … 1. The amount of charge that has been separated (coulombs) 2. The potential difference/voltage (volts)

2. Potential Difference (Voltage) The pushing force of water (electricity) is due to the …height difference (potential difference/Voltage) Voltage - like a “pushing force” of electricity - measured in volts (V) The potential energy in a battery is due to … 1. The amount of charge that has been separated (coulombs) 2. The potential difference/voltage (volts)

Which has greater potential difference (voltage)?

Electric Potential Energy & Electric Potential Difference The potential difference (voltage) in a battery is like… the height of the stairs The amount of potential energy (charge/Coulombs) separated in a battery is like… the mass moved up the stairs If this person were to fall from top of the stairs, in A or B, the potential difference (height) is the same However, there’s more potential energy in B than in A because more mass (charge/Coulombs) have been separated A B

The Voltmeter Measures Electric Potential Difference Voltmeters are a device that measures the amount of potential difference between 2 locations of charge separation In this image, The battery’s voltage is measured Volt (V) is the unit for measuring voltage

Batteries: Wet Cells or Dry Cells Electrolyte: Substance that conducts electricity Dry cell – moist paste Wet cell – battery solution

Producing Voltage Electrodes the 2 terminals of a battery 2 different metals (usually) Electrolyte Substance that conducts electricity Acid, base or salt In Figure 8.6 the acidic electrolyte… pulls atoms off the Zinc and leaves electrons on electrode pulls electrons off the Copper electrode

Sources of Electrical Energy 1.Friction 2.Piezoelectric Crystals 3.Photo-electrochemical cells 4.Thermocouples 5.Generators

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