Word Problems
A battery supplies 3,600J of energy to a circuit at 12V.
What is the charge required to achieve this energy?
300C
How do resistors regulate the current in a circuit, and what would happen if you removed a resistor from a circuit?
Total resistance will most likley decrease, increasing the current
During charging in electrostatics, why are electrons the only subatomic particle we are describing.
protons and neutrons are fixed and do not move in these processes
What does a fuse do in a circuit
Breaks the circuit if too much current flows
Rubbing a balloon on your head is an example of charging by ...
Friction
A laptop requires 1,200J of energy to operate, and it uses 15V to do so.
How much charge is required to provide this energy?
80C
What happens to the brightness of a bulb if more bulbs are added in series?
It gets dimmer (less current through each bulb).
which terminal do electrons flow out of in a battery?
negative
What does Kirchhoff’s Current Law say about currents at a junction?
The total current entering a junction equals the total current leaving.
Rubber and glass are examples of...
Insulators
A 4Ω resistor has 2 A of current passing through. What is the power?
16 W
What would happen if you connected a light bulb in series with a battery without a resistor? How would the circuit behave?
Without a resistor, the light bulb would draw excessive current, possibly burning out quickly, as there is nothing to limit the current flow. The battery could also be drained rapidly.
What materials make a good conductor and what materials make a good insulator?
Conductor: metals, graphite
Insulator: rubber, plastic, glass
If 2 A flows into a junction and splits into two branches, one with 1.2 A, how much current is in the other?
0.8 A
The rate at which electrical energy is used.
Power
A battery delivers 500J of energy to a circuit in 2 minutes (120 seconds) at a voltage of 10V.
What is the current flowing through the circuit?
50C, 0.417A
Solve for the unknowns:
V2= 3V, V4=9V, I3=1A I4=4A
during conduction, if a negative rod approaches a neutral object, what will happen to the neutral object?
transfers electrons to the neutral object, making it also negative, therefore, repelling
Explain why adding a resistor in parallel decreases the total resistance, even though you’re adding more components.
Because parallel paths provide more routes for current, reducing the total load on any one resistor.
2 examples of a control in a circuit
light switch and fuse
A device operates with a current of 2A for 30 minutes (1,800 seconds) at a voltage of 12V.
How much energy is consumed by the device?
3600C, 43200 J
Solve for the unknowns:
I1=0A, I2=10A, I3=10A, V1=0V, V2=0.5V, V3=1V
Why can birds sit safely on power lines without getting electrocuted?
Both of the bird’s feet are at the same electric potential, so there’s no voltage difference across its body, and no current flows.
Why must a fuse be connected in series and not in parallel?
In series, all the current passes through it. If the fuse is in parallel, current can bypass it, and it won't protect the circuit.
A short circuit and an example
A short circuit happens when there is an accidental connection with very little resistance between two parts of a circuit, skipping over the normal components. This allows too much current to flow, which can damage the circuit and possibly cause a fire. Example: if wires in a lamp accidently touched each other