The Following topics are the MAIN areas of study for this unit for both Foundation and higher level candidates. It is advised that these areas should be revised in more depth.

Static Electricity
Circuits
Power
Ohms Law
Components
AC and DC Current

Back to main Physics menu

Click here for detailed explainations of static electricity in use

a) Positive Charges = Protons
Negative Charges = electrons

b) Insulating Materials
can be charged by rubbing (negative charges move from one material to another)

c) Examples of Static (e.g. balloons sticking to a wall)

also

• Lightning
• Refuelling problems for aircraft (can be dangerous if refuelling in the air)
• Paint spraying
• Used in Photcopiers and Laser Printers
• Dusters etc

Any charged material brought up to the top plate will repel the charges down into the leaves making them push apart

back to top

---

2)CIRCUITS

1. Symbols and how to draw circuits

   COMPONENT	SYMBOL
   Battery
   Cell
   Bulb
   Ammeter
   Voltmeter
   Resistor
   Joined Wire

   Circuits must be drawn with complete loops (no gaps)



2. Current is measured in AMPS with an Ammeter (wired in series)
3. Voltage (Potential Difference) Is measured in Volts with a Voltmeter (Wired in Parallel)
4. Current is The Movement of Electrical charge (free electrons in metals)
5. Charge (Coulombs)= Current (amps)´ Time (s) (Q=I´ t)

back to top

---

3)ELECTRICAL POWER

Rate of using Electrical Energy

POWER	=	VOLTAGE	×	CURRENT
P	=	V	×	I
(watts)		(volts)		(amps)


back to top

---

4) RESISTANCE AND OHMS LAW

1. Resistance in a wire changes with length heat and thickness (Longer, thicker hotter = increased resistance)



2. Ohms Law:-
   

   VOLTAGE	=	CURRENT	×	RESISTANCE
   V	=	I	×	R
   (Volts)		(amps)		(ohms)


3. Series Circuits
Voltage is split between components current is constant
Total resistance (ohms)=R₁+R₂

4. Parallel Circuits
Voltage is constant across each branch current is split
Total Resistance (ohms) = (R_1´ R₂) ¸ (R₁₊R₂)

back to top

---

5) ELECTRICAL COMPONENTS

(Symbol and how they work)

COMPONENT	SYMBOL	HOW IT WORKS	What it is used for
Light Dependant Resistor		Made from Cadmium Sulphide (light Sesisive material. It's resistance changes with the amount of light (more light = Less resistance)	Light Sensor
Thermistor		Sensitive to heat. it's resistance changes with heat( more heat = Less Resistance	Temperature sensor
Diode		Allows current to flow through it in ONE DIRECTION only	AC to DC rectification, component protection
Capacitor		it stores Electrical charge	Timing, Smoothing ac, creating rf signal

back to top

---

6)AC AND DC CURRENT


Click here for details of why we get AC

AC-Alternating current the sort of current you get from the mains (looks like sine wave)

DC Direct current- the sort you get from batteries (flat line)


back to top

---