Transcript 16electricity review - Mr-Hubeny

Objective:
MCAS reviewElectricity
Homework:
Go to bed early
Eat a healthy breakfast
Take out MCAS O.R. question
Compare to other students’ work
What would you rate each?
What would you have scored?
Scoring Guide - Score Point 0
4
3
12
5 Main Topics of Electricity on
MCAS
 Circuits, Circuit diagrams, series vs. parallel
 Ohm’s Law and Electric Power
 Static Electricity: Induction and Contact
 Coulomb's Law
 Electromagnetism
circuit diagrams
In circuit diagrams components are represented by
the following symbols;
Some
battery
ammeter
Switch
Switch
(closed)
(open)
voltmeter
motor
lamp
resistor
diagrams use
the resistor
symbol as a
symbol for a
lamp or light
(since a light
bulb is in fact
a resistor!)
wire
Electrical Circuit
 A circuit is made up of a series of
components all connected together and
hooked up to a power source (such a a
battery)
 Any openings in a circuit and the circuit
will stop working! (open switch)
 Conductors like metal allow electricity to
flow, but insulators (such as wood, plastic,
rubber) stop flow of electricity.
SERIES CIRCUITS
The components are connected end-to-end, one
after the other.
They make a simple loop for the current to flow
round.
If one bulb ‘blows’ it breaks the whole circuit and
all the bulbs go out.
Voltage shared, current same
PARALLEL CIRCUITS
The components are connected side by side.
The current has a choice of routes.
If one bulb ‘blows’ there is still be a complete circuit to
the other bulb so it stays alight.
Voltage same, current shared.
Ohms Law Table
Resistance
Current
Voltage
to the flow of
charges
The flow of
electrons
through a
circuit
Potential
Difference
( the push
behind
electricity)
Symbol
R
I
Equation
R=V
I=V
I
R
Definition The opposition
V
V=IR
MCAS formula sheet only gives
one Ohm’s Law formula:
 V = IR
V
So, set up triangle to solve for rest:
Also do same for Power:
P = VI
P
V
I
Bringing Charges Together
+
+
+
-
-
Attract
-
+
+
-
-
Repel
Repel
-
-
-
-
+
Charging by
contact vs.
charging by
induction.
Contact
Charge by Induction:
-no contact
-no electron transfer
-charged by “influence”
Charge by Contact:
-contact by items
-electron transfer
-charged by gaining or
losing electrons
Coulomb’s Law
More charge = more force
(multiplying together)
More distance = a lot less
force (dividing by square of #)
When current flows through a wire
you get a electromagnet
 3 things make magnet
stronger:
- More current
- More loops
- Metal core