Producing and Measuring Electricity

8/6/2019 Producing and Measuring Electricity

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Producing and MeasuringProducing and MeasuringElectricityElectricity

W Richards

The Weald School

Edexcel


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Types of BatteriesTypes of BatteriesType of Battery Contains Uses

Wet cellrechargeable

Lead and acid Cars, industry

Dry cell

rechargeable

Nickel, cadmium,

lithium

Mobile phones,

power tools

Dry cell non-rechargeable

Zinc, carbon,manganese,lithium

Torches, clocks,hearing aids

Why use rechargeable batteries?

Long long-term expense

Can be used many times

Less energy to produce

Why use standard batteries?

No need for charger

Less expensive

Rechargeables contain carcinogens


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Battery CapacityBattery CapacityThe capacity of a battery is measured in Amp Hours (Ah).

Basically, a battery with a capacity of 1Ah will provide acurrent of 1A for 1 hour.

Capacity (Ah) = Current (A) x Time (hours)

1) A battery provides a current of 2A for 2 hours. What wasits capacity?

2) Another battery has a capacity of 10Ah. If it runs out

after half an hour what current was being drawn?

3) A mobile phone battery has a capacity of 1100mAh. If it

runs on a current of 250mA when being used in a phone callhow long could the call last?


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Electric CurrentElectric CurrentElectric current is a flow

of negatively chargedparticles (i.e. electrons). Note thatelectrons gofrom negativeto positive

-+ e-

e-


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Basic ideasBasic ideasElectric current is when electrons start to flow around a

circuit. We use an _________ to measure it and it ismeasured in ____.

Potential difference (also called _______) ishow big the push on the electrons is. We use a________ to measure it and it is measured in______, a unit named after Volta.

Resistance is anything that resists an electric current. It ismeasured in _____. It usually increases when a device getshot.

Words: volts, amps, ohms, voltage, ammeter, voltmeter


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More basic ideasMore basic ideas

If a battery isadded the currentwill ________because there is a

greater _____ onthe electrons

If a bulb is added

the current will_______ becausethere is greater________ in the

circuit


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ElectromagneticElectromagnetic

inductioninductionThe direction of the induced current is

reversed if

1) The magnet is moved in the opposite

direction2) The other pole is inserted first

The size of the induced current can be

increased by:1) Increasing the speed of movement

2) Increasing the magnet strength

3) Increasing the number of turns on

the coil


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Generators (dynamos)Generators (dynamos)

Induced current can beincreased in 4 ways:

1) Increasing the speed ofmovement

2) Increasing the magneticfield strength

3) Increasing the number of

turns on the coil4) Increasing the area of the

coil


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Georg Simon Ohm1789-1854

ResistanceResistance

Resistance is anything that willRESIST a current. It is measuredin Ohms, a unit named after me.

The resistance of a component can becalculated using Ohms Law:

Resistance = Voltage (in V)

(in ;) Current (in A)

V

RI


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An example question:An example question:

V

A

1) What is the resistance acrossthis bulb?

2) Assuming all the bulbs are thesame what is the total resistance

in this circuit?

Voltmeter

reads 10V

Ammeterreads 2A


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More examplesMore examples

12V

3A

3A

6V

4V

2A

1A

2V

What is theresistance ofthese bulbs?


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ResistanceResistance

Resistance is anything that opposes an electric current.

Resistance (Ohms, ;) = Potential Difference (volts, V)

Current (amps, A)

What is the resistance of the following:

1) A bulb with a voltage of 3V and a current of 1A.

2) A resistor with a voltage of 12V and a current of 3A

3) A diode with a voltage of 240V and a current of 40A

4) A thermistor with a current of 0.5A and a voltage of

10V


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CurrentCurrent--voltage graphsvoltage graphsI

V

I

V

I

V1. Resistor 3. Thermistor

2. BulbCurrentincreases inproportionto voltage

As voltage increasesthe bulb gets hotterand resistance

increases

Resistance goesdown as thethermistor getshotter (i.e.more voltage)

Low R

High R


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LDRs and ThermistorsLDRs and Thermistors


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LDRs and ThermistorsLDRs and Thermistors

2) Thermistor resistance DECREASESwhen temperatureINCREASES

1) Light dependantresistor resistanceDECREASES when lightintensity INCREASES

Resistance

Amount of light

Resistance

Temperature


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Electrical InventionsElectrical InventionsMatch these inventions with when they were invented:

Electric kettle

Telephone

Television

Electric fire

Electric ironVacuum cleaner

1876

1882

1891

1892

19081920s


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ComputersComputers

IBM 5100 portable PC (1975), 25kg,1.9MHz processor, 64K RAM, 200Kinternal tape storage, cost up to $20,000

Apple 1 (1976) 1Mhzprocessor, 4K RAM, cost $670

Commodore 64 (1982) 1Mhz

processor, 64K RAM, 16colours, cost $600, 17m sold Apple Macintosh (1984) 8Mhzprocessor, 512K RAM, cost $2500


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SuperconductivitySuperconductivity

Heike Kamerlingh

Onnes (1853-1926)

In 1911 I discovered superconductivity. Thisis when a metal can conduct electricity withzero resistance. I won the Nobel Prize for

this discovery in 1913.

The Maglev train is based on

superconductivity and usesmagnets to propel the train tospeeds of over 300mph.

Producing and Measuring Electricity

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