Electric Charge & Current
Which negatively charged particles move through a metal wire to create electric current?
Electrons.
What device is used to open or close an electrical circuit?
A switch.
What are the two poles of a magnet called?
North and south.
True or false: Electric current flowing through a wire creates a magnetic field around it.
True.
Which metal is commonly used for electrical wiring because it conducts electricity well?
Copper.
What is the unit used to measure electric current?
Amperes (amps).
What is the name for a complete path through which electric current can flow?
A closed circuit.
What happens when the north pole of one magnet is placed near the south pole of another?
They attract (pull toward each other).
What is the name of the invisible region around a magnet where magnetic forces can act?
A magnetic field.
Which material is a better conductor of electricity: cotton fabric or copper wire?
Copper wire.
What happens to an object's overall charge when it gains extra electrons?
It becomes negatively charged.
Name three essential components needed to light a bulb in a simple battery-powered circuit.
An energy source (battery), conducting wires, and a bulb (load), connected in a complete loop.
What happens when two north magnetic poles are brought close together?
They repel (push away from each other).
What happens to the magnetic field around a straight wire when the current through the wire increases?
The magnetic field becomes stronger.
Why does saltwater generally conduct electricity better than very pure water?
Dissolved salt forms mobile ions that carry electric charge through the water.
An object has 8 protons and 11 electrons. What is its overall charge?
−3, because it has three more electrons than protons.
Two identical bulbs are connected in series to one battery. What happens to both bulbs if one bulb is removed and the circuit is left open?
Both bulbs go out because removing one bulb breaks the only path for electric current.
Three magnets pick up 6, 20, and 50 identical nails under the same conditions. Which magnet shows the greatest magnetic strength?
The magnet that picks up 50 nails.
Why can wrapping a current-carrying wire into several coils create a stronger magnetic field inside the coil?
The magnetic fields produced by the loops reinforce one another inside the coil.
Describe the path electricity takes from a power station to a home.
Electricity is generated at a power station, sent through high-voltage transmission lines, passed through substations and transformers, then distributed through local power lines to homes.
Two objects begin electrically neutral. Electrons move from Object A to Object B. Explain the charge each object develops and why.
Object A becomes positively charged because it loses electrons. Object B becomes negatively charged because it gains electrons.
Two identical bulbs are connected in parallel to one battery. If one bulb burns out and its branch becomes open, what happens to the other bulb? Explain.
The other bulb can remain lit because it has its own complete branch connected to the battery.
A student uses a stronger magnet in an experiment to attract metal paper clips from below a thin surface. Predict what may change and explain why.
The stronger magnet may attract more paper clips or attract them from a greater distance because its magnetic field exerts a stronger force under comparable conditions.
An engineer wraps insulated wire around an iron nail to make an electromagnet. Describe two changes that could make it stronger and explain why.
Increase the number of wire turns so their magnetic fields reinforce one another, and increase the electric current to create a stronger magnetic field. Using a suitable iron core also helps strengthen the field.
A generator uses motion and magnetic fields to produce electricity. Explain how moving a magnet relative to a coil of wire can generate an electric current.
The changing magnetic field through the coil induces a voltage. If the coil is connected in a closed circuit, this voltage can drive an electric current.