Electricity test 12/A

Date of the test 3rd of February

1. Short history of electricity


Greek scientist, rubbing amber ήλεκτρον (electron) attracts small objects

Benjamin Franklin  In June 1752 he is reputed to have attached a metal key to the bottom of a dampened kite string and flown the kite in a storm-threatened sky. A succession of sparks jumping from the key to the back of his hand showed that lightning was indeed electrical in nature. In June 1752 he is reputed to have attached a metal key to the bottom of a dampened kite string and flown the kite in a storm-threatened sky. A succession of sparks jumping from the key to the back of his hand showed that lightning was indeed electrical in nature.

In 1791, Luigi Galvani published his discovery of bioelectricity, demonstrating that electricity was the medium by which nerve cells passed signals to the muscles. Alessandro Volta's battery,  of 1800, made from alternating layers of zinc and copper, provided scientists with a more reliable source of electrical energy than the electrostatic machines previously used.

Electromagnetism

On 21 April 1820, during a lecture, Ørsted noticed a compass needle deflected from magnetic north when an electric current from a battery was switched on and off, confirming a direct relationship between electricity and magnetism.

  Michael Faraday invented the electric motor in 1821.

In 1821, soon after the Danish physicist and chemist Hans Christian Ørsted discovered the phenomenon of electromagnetism.

Electromagnetism manifests as both electric fields and magnetic fields. Both fields are simply different aspects of electromagnetism, and hence are intrinsically related. Thus, a changing electric field generates a magnetic field; conversely a changing magnetic field generates an electric field.


 2. Phet simulation


http://phet.colorado.edu/en/simulation/faradays-law
http://phet.colorado.edu/en/simulation/faraday
http://phet.colorado.edu/en/simulation/generator (important)
http://phet.colorado.edu/en/simulation/magnets-and-electromagnets
http://phet.colorado.edu/en/simulation/circuit-construction-kit-dc (important)


Basic questions:


Build a circuit. One lamp, battery and a switch. What will be the current if the voltage of the battery is 15 V and the resistance of the bulb is 10 Ohm.


What happens if you increase the turns of the first or second coils in transformer?


Explain how does the generator work with the generator simulation?


What is the diffrences between bar and electromagnet? Explain it with the simulations.




3. BBC Bitesize 


You have to know the test.


Electric current and voltage

Video: http://www.bbc.co.uk/schools/ks3bitesize/science/energy_electricity_forces/electric_current_voltage/activity.shtml


Test: http://www.bbc.co.uk/apps/ifl/schools/ks3bitesize/science/quizengine?quiz=electricity&templateStyle=science


Magnets and electric current

Video: http://www.bbc.co.uk/schools/ks3bitesize/science/energy_electricity_forces/magnets_electric_effects/activity.shtml

Test: http://www.bbc.co.uk/apps/ifl/schools/ks3bitesize/science/quizengine?quiz=magnetism&templateStyle=science

 4. Your presentations


Electromagnets
Generator
Magnets (Earth magnetism)
Electric motor
Transformer


You have to know the basic things about them.


What is it?
How does it work?
What can be used for?

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What was Benjamin Franklin's  famous experiment?

Stromy weather, used a kite, key started to sparkle, proved that electricity in the cloud is the same as the electricity on earth
discovered that there are two types of charges


What did the Danish scientist Oersted discover?

if current flows in a wire it causes magnetic filed around the wire, 

How can you produce electricity? Write down 3 different methods.

1. rubbing
2. two diffrent metal in a special liquid, Volta battery
3. generator, magnet spins in a coil (Faraday)

What was the discovery of Faraday which revolutionized the technology?


electrical motor, generator

2. Which of the following is not a magnetic material?

steel
cobalt
aluminium

3. What do two poles of the same type do when they are brought close together?

they attract
they repel
they make an electric current flow

6. Where are the field lines most concentrated around a bar magnet?

at both poles
in the middle
at the north pole only

7. How can we increase the strength of an electromagnet?

add an iron core
reduce the number of turns on the coil
reduce the current in the coil

8. What is one difference between electromagnets and bar magnets?

Bar magnets can be turned off but electromagnets cannot.
Bar magnets have a magnetic field but electromagnets do not.
Electromagnets need electricity but bar magnets do not.

9. What can we use to find the shape of a magnetic field?

an electromagnet
a coil of wire
a compass

10. What two gases are produced from electrolysis of water?

magnesium and hydrogen
hydrogen and oxygen
oxygen and magnesium

11. What is NOT true about energy saving light bulbs?

they use less energy than normal bulbs
they transfer less of their energy into heat
they are brighter than normal bulbs

1. What needs to be done to this circuit so that the lamp lights up?

close the switch
add another lamp
add a cell and close the switch

2. What component does this circuit symbol represent?

cell
buzzer
capacitor

3. Which switch or switches must be closed to make the lamps light?

only switch 1
only switch 2
switches 1 and 2

4. If lamp 1 is unscrewed from its holder, what will happen to lamp 2?

it will get brighter
it will go out
it will stay the same brightness

5. If lamp 1 is unscrewed from its holder, what will happen to lamp 2?

it will stay lit
it will go out
it will get dimmer

6. What is wrong with this circuit diagram?

there is only one cell
the ammeter should be connected in series
a ammeter should be connected in parallel

7. Which ammeter will have the biggest reading?

ammeter 1
ammeter 2
they will read the same

8. Which statement about electric current is correct?

it always flows clockwise
it gets used up as it goes around the circuit
it does not get used up as it goes around the circuit

 
1. Build a circuit. One lamp, battery and a switch. What will be the current if the voltage of the battery is 15 V and the resistance of the bulb is 10 Ohm.


2. What happens if you increase the turns of the first or second coils in transformer?

 If you increase the number of turns the voltage will be bigger and if you decrease the voltage will be smaller

4. Explain how does the generator work with the generator simulation?

 something (water, steam)turns around a magnet and the spinning magnet induces AC current in a coil


5. What is the diffrences between bar and electromagnet? Explain it with the simulations.

you need electricity and you can switch off or on


Electromagnets
Generator
Electric motor
Transformer


What is it?
How does it work?
What can be used for?