Using Voltmeters and Ammeters www.assignmentpoint.com

Using Voltmeters and Ammeters Voltmeter – connected in parallel V A Ammeter connected in series www.assignmentpoint.com

Correctly Wired? No! The voltmeter has been connected in series – it should be parallel V www.assignmentpoint.com

Correctly Wired? No the Ammeter has been connected in parallel – it should have been series A www.assignmentpoint.com

Correctly Wired? Yes! This Ammeter has been connected correctly in series A www.assignmentpoint.com

Correctly Wired? Yes! This Ammeter has been connected correctly in series A www.assignmentpoint.com

Correctly Wired? V Yes! The Voltmeter has been connected correctly in parallel www.assignmentpoint.com

Correctly Wired? Yes! The Ammeter has been connected correctly in series A www.assignmentpoint.com

Effects of Series? As more bulbs are added in series the bulbs grow dimmer www.assignmentpoint.com

Circuit Diagram Iron Plastic Brass Rubber Copper Perspex Steel Glass Conductors Insulators Iron Plastic Brass Rubber Copper Perspex Steel Glass Graphite Wood www.assignmentpoint.com

Conducts doesn’t get hot Wire Observation Use Nichrome copper Tin-lead Electric fire Glows red hot Conducts doesn’t get hot Conducting wires Heats up and melts Safety fuse www.assignmentpoint.com

When the voltage increases the current increases Battery Battery voltage Bulb brightness 1. 2. 3. 1.5 V dim 6 V brighter 12 V bright When the voltage increases the current increases www.assignmentpoint.com

The more batteries the brighter the bulb 5. Write down your ideas. The more batteries the brighter the bulb This holds true as long as the batteries face the same way If batteries are reversed they cancel each other out Elephant handout www.assignmentpoint.com

Text Animation 1 www.assignmentpoint.com

Choosing the best type of cable Title: Aim: Method: Choosing the best type of cable To compare copper/nichrome, thick/thin, long/short wires and find the best Test thick and thin wires in a circuit and measure how it affects the current using an ammeter. Then test copper/nichrome and long/short wires. www.assignmentpoint.com

A bulb may be used instead of an ammeter Diagram: Results: A bulb may be used instead of an ammeter Wire Current long short copper nichrome thick thin www.assignmentpoint.com

Short wires are better than long wires. Conclusion: Short wires are better than long wires. Copper wires are better than nichrome wires. Thick wires are better than thin wires. www.assignmentpoint.com

Copper has a resistance than nichrome Thin wires have resistance than thick ones Longer wires have resistance than short ones lower higher higher www.assignmentpoint.com

4. Write down what you found out. The variable resistor 4. Write down what you found out. The longer the wire (coil) the dimmer the bulb, the shorter the wire the brighter the bulb. www.assignmentpoint.com

Write down what you found out. The variable resistor Write down what you found out. The longer the wire (coil) the smaller the current and the dimmer the bulb. The longer wire has a higher resistance. www.assignmentpoint.com

A long thin nichrome wire has a higher resistance because a) Thick copper wires are good for carrying current because b) Long thin coils of nichrome are used in electric fires because thick has a lower resistance, as does copper and short wires. copper is a good conductor and thick wires have low resistance nichrome has a high resistance causing it to heat up without melting www.assignmentpoint.com

the resistance wire is lengthened, causing a reduction in the current. 3. A variable resistor is used to 4. When the volume on a radio is turned Down 5. Cookers need thick cabling increase and decrease the current by changing the length of a resistance wire the resistance wire is lengthened, causing a reduction in the current. because they use much more current than lamps www.assignmentpoint.com

to protect you from a short circuit - safety The purpose of a fuse is to protect you from a short circuit - safety Not to make the device work www.assignmentpoint.com

Circuit Symbols (components used in slides) A V You can find more downloads and help at www.lab6.co.uk www.assignmentpoint.com