Electrical Circuits
What will cause an electrical circuit to both stop powering devices, and become an immediate fire hazard?
Short circuit
Yes or No: Franklin says that placing a strong magnet near a coil of copper wire will induce an electric current in that wire, but only if the magnet is inside of the coil.
Is Franklin correct?
No!
Induction of electrical current requires changing magnetic fields to push electrons through the wire.
(Use Position vs Time graph)
At what time(s) is the object at rest?
0s - 1s, 6s - 7s
Student A leaves his seat to use the bathroom, stopping at his locker, 3 classrooms, and the vending machine before returning to the same seat.
Is student A's distance or displacement greater?
Distance.
Displacement is 0, distance is greater than 0.
Which form of energy do spinning turbines have inside of power plants?
Kinetic/mechanical
A power plant that uses a spinning turbine will always produce ____________ current.
Alternating
Finish the sentence: velocity is a measure of how Position _________________.
changes over time.
Would this real-world problem use derivatives or integrals?
NASA is landing a rocket with people aboard on the moon and need to calculate the rocket's velocity every second as it nears the surface.
Derivatives: calculating rate of change for velocity
Explain simply how switches work.
A mechanical connection.
On: metal-to-metal connection
Off: breaks the circuit
A battery powered circuit will always produce _____________ current.
Direct
(Use Position vs Time graph)
Does this object have an acceleration from t = 3s to t = 6s?
No. Slope is constant, so the object has a velocity, but that velocity is not changing.
Would this real-world problem use derivatives or integrals?
A pandemic has broken out and scientists are recording how many new infections are occurring each day.
Integrals: we are taking sums of something that is changing over time.
Which unit is used to measure electric current?
Amperes (A)
When a copper wire enters a changing magnetic field, what is being induced in that wire?
Current
A position–time graph has a constant positive slope.
Velocity is: positive or negative
: constant or changing
Positive, constant
The position function of an car's movement is given by s(t) = 4t. What is the velocity function of the car?
v(t) = 4
Must take derivative
A sprinter runs at a constant velocity of 8 m/s for 4s. How far does the sprinter travel?
Vf = [(4s)(8 m/s + 8 m/s)] / 2
32m
A toaster produces 12 ohms (Ω) of resistance in 10 A circuit. What is the amount of voltage in the circuit?
120 v
(V = IR)
Describe electron behavior in magnets.
Electrons are all spinning in the same direction, creating an electromagnetic field.
In nonmagnets, electrons spin in random directions, so all the tiny electromagnetic fields cancel out.
(Use Position vs Time graph)
What is the object's velocity from t = 1s to t = 3s?
Slope = (y2 - y1) / (x2 - x1)
Slope = (-40 - 0) / (3 - 1)
Slope = -40 / 2
Slope = Velocity = -20 m/s
The position function of an asteroid's motion is given by s(t) = 2t2 + 8t + 10.
What is the acceleration function of the motion?
Must take derivative twice.
a(t) = 4
A truck accelerates from rest at 3 m/s2 for 5s. What is its final velocity?
vf = vi + at
vf = 0 + (3 m/s2)(5s) = 15 m/s