# PHYSICS

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PHYSICS

## 3. POTENTIAL DIFFERENCE / VOLTAGE

### 3.1. Measures the difference in electric potential between 2 points in a circuit

3.1.1. To measure, use a voltmeter between 2 locations in a circuit

3.1.1.1. SI unit is VOLT (V)

6.1.1. Aluminum

6.1.2. Copper

6.2.1. Moist Air

6.2.2. Carbon

6.3.1. Rubber

6.3.2. Plastic

## 7. CHARGING OBJECTS

### 7.1. 1. ONLY ELECTRONS MOVE FROM ONE OBJECT TO THE OTHER                                     2. OPPOSITE CHARGES ATTRACT                   3. SIMILAR CHARGES REPEL

7.1.1. TOUCH

7.1.1.1. Electrons can be transferred through contact or touching a charged object to a neutral object.

7.1.1.1.1. The neutral object gains the same type of charge as the object that has touched it.

7.1.1.1.2. They both end up with similar charges so they repel.

7.1.2. FRICTION

7.1.2.1. The force resisting the relative motion of two surfaces in contact with each other

7.1.2.2. The force of friction can remove electrons from one object and cause them to transfer to the other

7.1.3. INDUCTION

7.1.3.1. The movement of electrons within a substance  caused by a nearly charged object, without direct contact

7.1.3.2. Induced charge is USUALLY a temporary charge

7.1.3.2.1. is only detected as long as the charged object comes close to a neutral one

### 7.2. NEUTRAL OBJECTS ARE ATTRACTED TO CHARGED OBJECTS

7.2.1. THIS IS BECAUSE OF THE TEMPORARY CHARGE CAUSED BY INDUCTION

7.2.1.1. NO ELECTRONS LEAVE BUT THEY DO MOVE AROUND THE AREA, CREATING A TEMPORARY CHARGED AREA IN THE NEUTRAL OBJECT

## 8. CELLS

### 8.1. ELECTROCHEMICAL CELL

8.1.1. Package of chemicals that convert chemical energy  into electrical energy that is stored in charged particles

8.1.1.1. Electrodes

8.1.1.1.1. Metal strips that react with the electrolyte

8.1.1.2. Electrolyte

8.1.1.2.1. A liquid or paste that conducts electricity

### 8.2. DRY AND WET CELLS

8.2.1. WET CELL

8.2.1.1. An electrochemical cell that has a liquid electrolyte

8.2.2. DRY CELL

8.2.2.1. An electrochemical cell uses a paste electrolyte

8.2.2.2. SHOULD BE RECYCLED RATHER THAN THROWN IN THE TRASH

8.2.2.2.1. Some dry cells are rechargeable, can be reused multiple times which has less impact on the environment than non-rechargeable dry cells

8.2.2.2.2. Contains toxic materials

### 8.3. FUEL CELL

8.3.1. An electrochemical cell that generates electricity directly from a chemical reaction with a fuel

## 9. CIRCUITS

### 9.1. Path for electrons to flow.

9.1.1. Includes

9.1.1.1. Energy source

9.1.1.2. Conductor

### 9.2. There are 2 different types of circuits

9.2.1. SERIES

9.2.1.1. Only one path for the current to flow

9.2.1.1.1. If the path is broken, the whole circuit cannot function

9.2.1.2. Voltage: Vs = v1 + v2 + v3

9.2.1.3. Current = Same for all 3

9.2.2. PARALLEL

9.2.2.1. More than one path for the current flow

9.2.2.1.1. Due to multiple paths, an interruption in one path will not affect the other pathways

9.2.2.2. Voltage = Same for all 3

9.2.2.3. Current = Is = I1+ I2 + I3

## 10. CURRENT ELECTRICITY

### 10.2. The electricity produced by the continuous flow of electrons

10.2.1. In order for this flow to happen two things are required which forms an electrical circuit

10.2.1.1. AN ENEGRY SOURCE

10.2.1.1.1. Such as Battery or electrochemical cell

10.2.1.2. A COMPLETE PATH

10.2.1.2.1. Created by connecting wires

10.2.2. Other parts include LOADS and SWITCHES

10.2.2.1. LOADS are devices which convert electrical energy into another form of energy, like a light bulb

10.2.2.2. SWITCH can turn a circuit on and off by connecting and disconnecting the circuit

## 11. CURRENT

### 11.1. A device called an ammeter measures current

11.1.1. Alternating Current

11.1.1.1. Electric current flows back and forth at regular intervals called cycles

11.1.2. Direct Current

11.1.2.1. The current only flows one direction

### 11.2. SI unit current measured in is ampere (A)

11.2.1. A measure of the amount of charge moving past a point in the  circuit every second

## 12. RESISTANCE

### 12.2. All substances resist electrons to some extent

12.2.1. Conductors - Allows electrons to flow freely through them and low resistance values

12.2.2. Insulators- Resist electrons to flow and have a high resistance values

### 12.4. Measured by a device called an ohmmeter

12.4.1. SI unit = ohms (R/

## 13. RESISTOR

### 13.1. Any material that can slow down current flow

13.1.1. Is used in televisions, light bulbs, water pipes, etc.

## 14. FACTORS THAT CAN AFFECT THE RESISTANCE OF A WIRE

### 14.1. MATERIALS

14.1.1. Silver has the least resistance but is very expensive

14.1.2. Most conducting wires are made from copper

### 14.2. TEMPERATURE

14.2.1. As the temperature of the wire increases, the resistance increases

14.2.2. Conductivity decreases

### 14.3. LENGTH

14.3.1. Longer wires offer more resistance than shorter ones

14.3.2. If the wire doubles in length, resistance doubles

### 14.4. CROSS-SECTIONAL AREA

14.4.1. Wider wires offer less resistance than thinner wires.

14.4.1.1. If the wire doubles in width, its resistance is half as great

14.4.2. Conducting wires that carry large currents need large diameters to lessen their resistance

16.2.1. V=IR

16.2.2. I = V/R

16.2.3. R= V/I

## 17. GENERATING ELECTRICITY

### 17.1. RENEWABLE AND NON- RENEWABLE SOURCES

17.1.1. RENEWABLE = Can be re-used multiple times before throwing out

17.1.2. NON RENEWABLE= Can be used only once

### 17.3. Generators transform the energy of motion into an electric current. The magnets inside a generator are rotated by a turbine

17.3.1. Turbine = A machine that uses the flow of a fluid to turn a shaft