Transcript Unit: Electricity and Magnetism Topic(s): Circuit

Electricity Unit 2
Topic(s): Circuit Basics and Friends
Learning Goals:
•Discuss the relationship between voltage, current, resistance, and
power in a DC Circuit
•Discuss the role of batteries, capacitors, and resistors in a circuit
•Define and describe conventional current
•Predict the impact on capacitance/resistance of a material by altering
its physical properties
•Analyze power situations and apply the appropriate equation
•LG #12 (there is too much to write here...)
Circuits at a glance…
• A complete circuit is a closed path for a charge to
follow.
• A voltage source (potential diff) is needed to
“make” the charge go
• A moving charge is called current
• “Stuff” that gets in the way of the moving charge is
called resistance (or resistors)
• “Stuff” that collects/stores charge are called
capacitors
Batteries
• Batteries provide a potential difference (one
terminal is at 0V)
• Charges move out of the + end of the
battery and go towards the – end
• Aligning batteries can make a big battery
(in your calculator and other things)
Battery
Current
• Current is moving charge (the video talks of
batteries being electron pumps).
• Conventional Current: We pretend that + charges
are the things that move to create current.
• Depending on how the current is created it can be
direct current (DC, from batteries) or it can be
alternating current (AC, from the wall)
• Units are C/s or A (for Ampere)
Resistance
• Things can get in the
way of the moving
charge.
• Physical
characteristics can
play a part in
resistance (insulators
and conductors)
• p 508 table of
resistivity.
Temp and Resistance
Ohm’s Law
• Some materials obey a
linear relationship
between voltage and
resistance
• These items are called
Ohmic
• Ohm’s law can also be
used to determine total
current in a circuit, voltage
drop in a circuit element,
and lots of other swell
stuff.
Electric Power
• Rate of converting electrical
energy
• Units [Watts]
• Operating power under
ideal conditions
• 1st equation is on AP
sheet. Remaining
equations are derived using
1st and Ohms Law
To Sum things up
These equations are fairly simple and they will serve as
the building blocks for DC circuit analysis
Ohm’s law will be as useful as Fnet was. You may use
the equation 3 or more times in a solution. You will want
to use subscripts to keep track of resistances, voltages,
and currents.
Our investigations will consist of ideal (word problems)
and non-ideal (real world).
Read carefully
Draw sketches/diagrams with proper labels