Electricity

Check and Reflect (p. 278) 1. Protons are found in the nucleus of the atom, and positively charged. Electrons circle the nucleus, and are negatively charged. 2. ‘Statically charged’ means an object has an excess of a particular charge. 3. VDGs build up static charge by using friction. A source of charge is rubbed against a belt, and the belt transfers the charge to a sphere at the top of the VDG. 4. A) like charges repel b) unlike charges attract

Check and Reflect (p. 278) 5. As you acquire electrons from the carpet, you become negatively charged 6. Sometimes we describe a neutral object as uncharged, meaning that there is not net charge. If we want to be more technically accurate, we may note that there actually are charges in a neutral object, but positive and negative charges are in equal portions.

Check and Reflect (p. 278) 7. A charged object will cause charge separation in a neutral object. 8. The plastic is neutral. When the negatively charged rod approaches, positive charges in the plastic are attracted to the negatively charged rod, so the plastic ‘jumps’ to the rod. But once the plastic contacts the rod, electrons move into the plastic, giving it a net negative charge, so it now repelled by the negative rod.

Recall What is static electricity ?

Which of the following statements about electrical charges is incorrect? A) positive charges attract negative charges B) negative charges attract neutral objects C) positive charges attract neutral objects D) negative charges attract negative charges

Which of the following statements about electrical charges is incorrect? A) positive charges attract negative charges B) negative charges attract neutral objects C) positive charges attract neutral objects D) negative charges attract negative charges

When balloons X and Y were suspended from the ceiling in a science classroom, they moved away from each other.

In the diagram below, two balloons, 5 cm apart, are suspended from a string

Illustrate why a balloon rubbed with fur sticks to a wall.

Electric Eels Electric eels produce static electricity that build up and discharge. They contain thousands of modified muscle cells called electroplaques, which can produce electricity. When the cells combine their electricity, the eel can produce a shock strong enough to take down a horse.

Current Electricity Section 1.2

Electric Currents Electrical currents flow under 2 conditions. It needs: 1)  an energy source. 2)  a complete path to flow through. This is called a circuit. Circuit – complete path that electrons flow through. There are two types: Series and parallel

Circuits Two types: Series circuit- electricity follows only one path Parallel circuit- electricity can go alternative routes Most electrical currents involve solid metal wires (why? better conductors of electricity) ** A circuit usually includes a conductor, an energy source, a load, and a switch Load – device in a circuit that converts electrical energy to another form of energy (e.g., Light bulb, motor, buzzer).

Let’s Play With Circuit Boards! Can you… Make a series circuit? What is your load? Make a parallel circuit? What are your loads? Making a parallel circuit, turn on the motor, and flick on/off the light(s)? Make the light bulb brighter? Use a foreign metal object (ex. Jewellery) to complete a circuit Use a foreign non-metal object to complete a circuit? What happens? Why?

Common Conductors and Insulators

Conductors A key problem with transferring electricity is how to move the charge. Conductors – a material that electric charge can move through easily. (ex. Wire) What is an insulator then? What possesses some items to be good conductors and others good insulators? Hint: think atomically with the Bohr model.

Amperes Amperes(A) is the unit of electrical current Most appliances in a home uses less than 15 A. 60 W light bulb = 0.5 A Microwave = 5 – 8 A Electric Kettle = 13 A Wristwatch = less than 1 A Amps are like the amount of water flowing over a waterfall Machine to measure is called an ampmeter

Volts Volt – the unit of voltage. Voltage is like the Height of a waterfall For safety reasons most devices use low voltage. Flashlight = 6 V Portable Stereo = 6 V Car electrical system = 12 V Wall sockets = 120 V Industrial machinery = 600 V Electrical transmission lines = 100 kV

Electrical Energy and Voltage Electrical Energy – the energy of electrons; transferred when electrons travel from place to place. Voltage – a measure of how much electrical energy an electron has. Potential Difference – change in the potential energy of electric charge compared to its potential energy at a reference point, such as the ground.

Measuring Voltage Voltmeter – instrument for measuring potential difference in volts. The are many types of voltmeters, the main difference is how sensitive it is, whether it measures mV, V, or kV. It is also important to connect the correct lead to the correct terminal to prevent damaging the sensitive needles. Red goes on + Black goes on -

Let’s Play With the Circuit Boards Again! Create a series circuit with a light bulb as a load. How many amps are in it? How many volts? Create a series circuit and make the light bulb go brighter. Now how many amps are in it? Now how many volts?

Homework P. 283 #1-8 READ UNIT D SECTION 1.3 We will NOT be doing this together!!!