Physics - Electrostatics, Drift Velocity, Circuits

Difference between EMF and Terminal potential difference

See pic

Define watt

Define current, charge (give equation too) and coloumb

Define potential difference

Define volt and coulomb

See pic

In terms of circuits, Give equation for voltage using work (W)

State Kirchhoff’s Laws

See pic

EMF equation

What is a galvanometer

A galvanometer is a tool that shows if a small electric current is flowing in a circuit.(often used in Wheatstone bridge)

What is a Wheatstone bridge

A Wheatstone bridge is a circuit (double potential divider) used to figure out an unknown resistance by comparing it with known resistors.

What is internal resistance

Internal resistance is the resistance inside a cell or power supply that opposes current flow

What is a potential divider

A potential divider is a circuit used to produce a small potential difference from a larger one.

Describe how to used a potential divider as a source of fixed or variable potential difference.

A potential divider uses two resistors in series across a voltage supply to produce fixed or variable output voltage.

To get a fixed potential difference, use two fixed resistors to provide an output voltage.

To get a variable potential difference, replace one resistor with a variable resistor (like a potentiometer), which allows the output voltage to be adjusted.

Derive the equation for resistors in series

Derive the equation for resistors in parallel

Derive the potential divider equation

Wheatstone bridge equation

Steps on how to use Wheatstone bridge

Potentiometer equation

What’s a potentiometer

A variable resistor used to measure unknown EMF or potential difference

(It allows you to adjust the resistance by turning a knob or sliding a control, which changes the output voltage.)

Advantages of using a potentiometer

Disadvantages of potentiometer

Define resistance and the ohm

Resistance - the measure of the opposition to the glow of current

Ohm - the unit for resistance

Ohm’s Law

For an ohmic conductor, the voltage across the conductor is directly proportional to the current flowing through it

Sketch an I-V graph for a filament lab

Sketch an I-V graph for a ohmic conductor

Sketch an I-V graph for a semiconductor diode

Define resistivity and state the equation and provide unit

Resistivity (ρ) is the resistance of a material per unit length and cross-sectional area.

How to strengthen the resistance or a wire (and provide an expression for each)

• Make the wire Longer

• Make the wire thinner

define Drift velocity

And derive an expression for it

• Drift Velocity - mean amount of velocity of the electrons flowing through a conductor when an electric field is applied.  

• Expression for drift velocity:

( I nevAAA!!! ) 

Derive: the equations from the picture

Draw the symbol for:

Draw the symbol for:

Draw the symbol for:

Draw the symbol for:

How many types of charges

• There are two types of charges. Positive and Negative changes. Objects can also be neutrally charged 

Explain charging by friction and give 3 examples

• Charging by friction - making physical contact in motion with two oppositely charged objects to transfer/exchange charges. (Charge is conserved because no charge was lost) 

Explain charging by induction and give 3 examples

• Charging by induction - bringing two neutrally charged objects into close proximity to make the charges in each object separate. One object is then grounded to release the negative charges to the ground.  Charge is conserved because no charge was lost) 

Like charges repel and unlike charges attract

Distinguish amongst conductors, semiconductors and insulators

• Conductors: materials that conduct electricity 

• Insulators: materials that are poor conductors of electricity 

• Semiconductors: in between

Explain electrostatic application in terms of

• Electrostatic crop spraying

• Electrostatic paint spraying

Explain electrostatic application in terms of

• Photocopiers

• Laser printer

Explain electrostatic application in terms of

• Dust extraction

Discuss 3 Hazards causes by charging by friction

1. Static shocks: You may feel a shock when touching a metal object after walking on carpet (due to charge buildup).

2. Fuel explosions: Refueling planes can cause sparks from static electricity, which may ignite fuel.

3. Lightning:

  - Thunderclouds build up huge static charges.

  - When the charge is strong enough, it discharges as lightning, possibly damaging buildings or killing people.

  - Lightning rods safely direct the charge into the ground.

- Electrostatic discharge (ESD): Can damage electronics or cause fires in flammable environments.