Download presentation
Presentation is loading. Please wait.
1
Electricity & Magnetism
Unit 2 Electricity & Magnetism
2
Expected Performances
D4. Explain the relationship among voltage, current and resistance in a simple series circuit. D5. Explain how electricity is used to produce heat and light in incandescent bulbs and heating elements. D6. Describe the relationship between current and magnetism.
3
Electricity Electricity: energy due to the movement of electrons through a material. Discovered by Ben Franklin.
4
Two types of electricity
Static electricity: electricity involving a build-up of stationary charges. Current electricity: electricity involving the flow of e- through a material.
5
Static Electricity The accumulation of excess electrical charge on an object. To create static electricity electrons are transferred between materials, by friction/rubbing causing one material to build up an excess of electrons, while a second material ends up with a shortage of electrons.
6
- charge = material with excess of electrons
+ charge= material with shortage of electrons If these charges become large enough the electrons jump from – to + creating a spark (lightning)
7
Law of charges: Like charges repel, unlike charges attract.
“Likes repel. Opposites attract.”
8
Law of Conservation of Charge
Electrical events simply rearrange the charges (move them from one object to another object, but the total charge remains constant)
9
Charged objects are surrounded by an electrical field that is similar to magnetic fields.
Electrical Field – Area around a charged object where its affects can be noticed.
10
Static charges are not noticed until something interacts with their field or they move by:
1. Conduction: a material that can carry e- that comes in contact with a charged object resulting in an electron flow (static discharge).
11
2. Induction: an object’s e- shift due to the presence of an electric field
12
Ohm’s Law Voltage, current and resistance are all related to each other by a formula called Ohm’s Law, developed by George Simon Ohm in 1827. Current = Volts/ Resistance I= V/R
13
Current Current: rate at which e- move past a point in a wire.
Unit: ampere (amp or A)
17
Voltage Voltage: the difference in electrical potential between two points. Unit: Volts (V) Voltage provides the force that causes e- to flow through a circuit. An increase in voltage causes an increase in electron flow.
18
VT = V1 + V2 + V3
19
Resistance Resistance - opposition of a substance to a flow of electrons. Unit: Ohms Ω The higher the resistance; the lower the current.
20
Factors Affecting Resistance
Material Thickness of a wire Length of a wire Temperature
21
Power Power: The rate at which energy is transferred or used in an electrical circuit. Unit: Watts (W)
23
Steps to solving Word Problems:
Read the problem 2. List all known values with their units 3. Write out equation with unknown isolated 4. Plug in #’s with units 5. Solve, give answer with PROPER UNIT!
24
Formulas Current = Volts/ Resistance I= V/R
Power is a function of Voltage and current expressed by the equation. P = V x I
26
Sample Problem #1 What is the current passing through a 3 W resistance that is connected to a volt battery?
27
Sample Problem #2 A 30 amp current is passing through a 4 W resistor, what is the voltage in the circuit?
28
Sample Problem # 3 A 6 v battery pushes electrons through a circuit with a current of 0.3 amps, what is the resistance of this circuit?
30
A 12 v battery causes a 0.3 amp current to pass through a bulb.
Sample Problem #4 A 12 v battery causes a 0.3 amp current to pass through a bulb. A) What is the bulb’s power usage? B) What is the resistance of the bulb?
31
What is the resistance of the bulb?
Sample Problem #5 How much current passes through a 40 W bulb attached to a 120 v power source? What is the resistance of the bulb?
32
What is the resistance of the bulb?
Sample Problem #6 A 100 W bulb has a 0.2 amp current passing through it, what is the voltage of the power source? What is the resistance of the bulb?
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.