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1. What happens to a compass needle when it comes in close contact of an electric current? What happens when that current is reversed? When no current is present, all the compass needles will point in the same direction (toward Earth’s magnetic field). When there is a current present, all the compass needles move to align with the magnetic field created by the electric current. If the current is reversed, each needle will point in the opposite direction. ● Figure shows how the magnetic field around the current-carrying wire forms a circle around the wire. 2. Explain the right-hand rule. Why is it used? “If you hold a wire in your right hand and point your thumb in the direction of the positive current, the direction that your fingers curl is the direction of the magnetic current.” This rule is used to determine the direction of a magnetic field; clockwise or counterclockwise. Keeping in mind that the direction of the electric current is OPPOSITE to the direction that the electrons are flowing!!! ● Current through wire is moving upward (electrons are moving downward) and magnetic field is moving counterclockwise because that is the direction of the right hand finger curl. ● Increasing the current will INCREASE the magnetic force. ● The net force being exerted is perpendicular to the current. 3. Why is a solenoid used to create a stronger magnetic field? What does it resemble? To increase the magnetic force from the presence of a current, without increasing the current (because that is often dangerous), you can wrap a wire into a coil. This is called a solenoid and it is MUCH safer. By creating a solenoid, the magnetic field of each loop of wire adds to the strength of the magnetic field of any neighboring loops. Thus creating a stronger magnetic field, similar to a bar magnet. ● More loops and a stronger current will create a stronger magnetic field. 4. What is an electromagnet? Why is it used? By inserting a rode made of magnetic material, such as iron, through the center of the coils in a solenoid, the strength of the magnetic field can be increased. This is called an electromagnet. ● The magnetic field of the solenoid caused the rod to also become a magnet. ● An electromagnet is STRONGER magnet than a solenoid because the rod adds to the coil’s magnetic field. 5. How do electric motors work? Electric motors are machines that convert electrical energy into mechanical energy. They can perform work when attached to an external device. These can be found in many devices around your home (toys, washing machines, dryers, fans, etc.) ● Commutator causes current to change direction. Thus causing the magnetic field to change direction as the coil spins. This needs to happen because the repulsion of the north and south poles surrounding the coil. Without this constant change in direction, the loop would simply bounce back in forth in the magnetic field until the force of friction caused the loop to come to a rest. Because the current keeps reversing, the loop rotates in one direction. Cause Effect Current in the coil Magnetic field Magnetic field of wire Wire spins Slits in the commutator Change in direction of current Reversal of current Wire rotates in one direction 6. How does a galvanometer work? A galvanometer is a device used to measure current. It consists of a coil of insulated wire wrapped around an iron core that can rotate between poles of a permanent magnet (an electromagnet). This can also function as an ammeter, which measures current and voltage. ● The magnetic field of the electromagnet interacts with the magnetic field of the surrounding permanent magnet, resulting in a force that turns the core, which moves a needle along a scale to show current in amperes.