Electricity and Magnetism Electric Charge Net electric charges

Electricity and Magnetism

Electric Charge • Net electric charges result from an imbalance of protons and electrons • • More electrons than protons = negative charge More protons than electrons = positive charge • Like charges repel and opposite charges attract • A neutral object is attracted to a charged object

Transfer of Electric Charge • Charge results when electrons are transferred; protons always stay in the nucleus • Induced charge- charges redistributed without changing net charge • Charged by contact- electrons are transferred from a charged object to a neutral object • Charged by friction- electrons transfer as surfaces rub together, results in static electricity

Ohm’s Law •

1. The headlights of a typical car are powered by a 12 V battery. What is the resistance of the headlights if they draw 3. 0 A of current when they are turned on? 2. A 1. 5 V battery is connected to a small light bulb that has a resistance of 3. 5 Ω. What is the current in the bulb? 3. The current in a video game is 0. 50 A. If the resistance of the game’s circuitry is 12 Ω, what is the voltage of the battery?

Circuits • When a load, such as a light bulb, is connected across a source of voltage it is called a closed circuit • Without a complete path, it is called an open circuit

Series vs. Parallel Circuits •

Total Resistance

Total Resistance

Total Resistance

Total Resistance

Magnetic Fields • Magnetism is caused when electrons align in the same way. • Magnets have a north and south pole. • Like poles repel; opposite poles attract. • Magnetic field lines form loops from north to south pole. • The field is strongest near the magnet’s poles.

Earth’s Magnetic Field • Compasses align to earth’s magnetic field. • Earth’s geographic north pole is actually its magnetic south pole. This is why compass needles point north (opposites attract).

Electromagnets • Moving electric charges produce magnetism • A solenoid is a coil of wire with an electric current running through it. • • More loops of wire = stronger magnetic field More current = stronger magnetic field • A rod of magnetic material like iron can be inserted through the solenoid to increase its strength and create an electromagnet.