Current, voltage, resistance Chapter 8 Current, Voltage and Resistance Science 9 Current, voltage, resistance

Objectives After you have completed this chapter you will able to: Explain how electric current results from the separation of charge and the movement of electron. Apply the laws of static electricity to electron flow in a circuit. Define: Voltage, Current and Resistance Draw circuit diagrams using appropriate symbols. Distinguish between potential and kinetic energy – static electrical energy and current electricity and conventional current and electron flow.

Section 8.1 Electrical potential energy and voltage Where can batteries be found? Watches Cell phones Laptops iPods Clocks Vehicles Remote control Radio controlled cars

BATTERIES In order for electricity to be useful it must be stored and controlled. One of the most common techniques to store electricity is a battery. A battery is a collection of smaller units called electrochemical cells, which convert chemical energy to electric energy.

In these cells, the positive and negative charges are separated resulting in terminals where connections are made. When the terminals are connected, electrons at the negative terminal travel to the positive terminal (opposite charges attract).

Every battery has two terminals called electrodes Every battery has two terminals called electrodes. Each electrode is usually made up of a different metal that is surrounded by a substance called an electrolyte, which conducts electricity between the two electrodes (positive is called the cathode, negative is called the anode).

Dry Cell battery

Wet cell battery

Different types of batteries Alkaline Lithium ion Silver oxide Nickel cadmium Nickel metal hydride

Common electrodes Zinc Nickel Copper Magnesium Lithium

Acids Bases Salts Ammonium chloride Potassium hydroxide Common electrolytes Acids Bases Salts Ammonium chloride Potassium hydroxide

Define energy ENERGY is the ability to do work (e.g. to go from potential energy to kinetic energy).

Kinetic v. potential energy Kinetic energy is the energy of motion. Potential energy is stored energy. Ex. A battery stores electrical energy until needed so a battery is said to have electrical potential energy.

In electricity we use a special form of potential energy called electrical potential. The amount of electrical potential per one coulomb is called the potential difference or voltage. The unit for measuring potential difference is the volt (V), named after Italian physicist Allesandro Volta. He invented the first battery, the voltaic pile.

How does a battery produce a potential difference Read page 273 to find out!!!

What is a voltmeter? A voltmeter is a device that measures potential difference (voltage) in a circuit. We use the symbol to represent a voltmeter in a circuit drawing.

How to use and read a voltmeter To use a voltmeter you connect one end of the device to one side of the battery (red to positive) and the other end to the other side of the battery (black to negative). If the voltage you get is negative, you have your connections backwards. To read a voltmeter, you simply read where the needle points on the scale. Make sure you read the correct scale!