Physics Topic 4, Static Electricity and Electricity (Y9+10)

Like charges…

REPEL

Opposite charges…

ATTRACT

where is there highest energy

energy shell furthest from the nucleus

when can an electron move UP a level

when electromagnetic radiation is ABSORBED

when can an electron move DOWN a level

the electron can EMMIT electromagnetic radiation

Static charge

the charge caused by an imbalance of protons and electrons on an object. Is caused by electrons being moved between objects by FRICTION

Polythene and Acetate rods with cloth dusters

Examples of static electricity

• Polythene rod > negatively charged (gained electrons)

• Acetate rod > positively charged (loses electrons)

electrostatic force

electrically charged objects exert a force on each other (attract/repel)

induced charge

a charge that is produced on an uncharged object or surface due to the proximity of a statically charged object. This charge is lost when the charged object is moved away.

examples of USES of static electricity

• electrostatic paint sprayers: paint droplets have the same charge so repel each other evenly, the object they are painting has the opposite charge (attract)

DANGERS of static electricity

• lightning > friction between water particles

• air plane static > friction between plane and air, plane gets charged

earthing

removal of excess charge on an object

• connects a charged object to the ground using a conductor (copper wire)

electric field

area around a charged object where it will experience a force

Current

The rate of flow of electrical charge, value is the same on a closed loop, measure using an Ammeter

Charge equation

Charge (coulombs) = Current (A) x Time (s)

Potential Difference

the energy supplied between two points in a circuit, shared between components in a loop, measured using a Voltmeter connected in parallel

Energy equation

Energy(J)= Potential Difference (V) x Charge (C)

resistance

opposition to current (ohms)

what is resistance caused by

electrons colliding with ions in the lattics which reduces current

Ohm’s Law

V = I x R

Potential Difference (V) = Current (A) x Resisitance (Ω)

CORE PRACTICAL: p.d, current, resistance of a component

• investigate relationship using a filament bulb

• relationship can be shown on an I-V graph

Resistor I-V graph

• directly proportional

Filament Lamp I-V graph

As current increases so will temperature which will increase resistance making the graph CURVED

Diode I-V graph

current only flows through a diode in 1 Direction

Light Dependent Resistor (LDR)

as light intensity increases, resistance decreases

• used in night lights, automatic lights

Thermistor

as temperature increases, resistance decreases

• used in thermostats and temperature detectors

CORE PRACTICAL: Series and Parallel Circuits

Measure current and p.d of the components as the output p.d from the power supply is changed

Series vs parallel Circuit practical CONCLUSION

• in a parallel circuit, filament bulbs shine brighter and operate independently because each branch receives the full source potential difference

• in series circuit, the bulbs share the potential difference and are dimmer.

Power Equations (x3)

• Power = Energy/ Time

• Power = p.d x current

• Power = current² x resistance