- Lightning Have you ever seen lightning hit the ground?Lightning is a large static discharge-a transfer of charge between two objects. It happens if there is a buildup of static electricity. A large amount of static electricity is formed when air moves around in thunderclouds. Areas of positive and negative charge build up. When enough charge builds up, there is a static discharge between the cloud and the ground. As the electric charges move through the air, they run into atoms and molecules, making the atoms and molecules light up. Thunder Lightning makes a bright light. It also creates powerful sound waves. Thunder is the sound that lightning makes The electrical energy in a lightning bolt rips electrons off of atoms in the air. This causes great amounts of heat.The air temperature around a lightning bolt can be as high as 30,000^circ C. The heat makes the air around the lightning bolt move faster. This rapid movement of air produces the sound waves that you hear as thunder. 9. Describe What is lightning? __ __ __
- 3) A bicycle wheel has an initial angular velocity of 1.50rad/s. If its angular acceleration is constant and equal to 0.200rad/s^2 what is its angular velocity after it has turned through 3.50 revolutions. 3.32rad/s
- Charging by Contact Just like the clothes in the dryer, when two materials are rubbed together, electrons can be transferred between them One object will have a negative charge. The other will have the same amount of positive charge Charging by contact is the transfer of charges by touching or rubbing. Charging by Induction Remember, electric forces change when objects move closer together. If a charged object is moved near a neutral object, electrons on the neutral object will move around. Suppose you charge a balloon by rubbing it with a cloth. If you bring the negatively charged balloon near your sleeve the extra electrons on the balloon repel the electrons in the sleeve. The electrons near the sleeve's surface move away from the balloon, leaving a positively charged area on the surface of the sleeve. A charged object rearranging the electrons on a nearby neutral object is charging by induction. Get It? 8. Contrast charging by contact with charging by induction. __ __ __ __ __
- Problem Solving (23 marks) 26. The distance between the second and sixth crests in a wave is 75 cm, and one crest travels a distance of 25 cm in 3.0 s. Find the frequency of the wave. (4 marks) 27. A sound wave with a frequency of 1.25times 10^4 Hz travels at 344m/s What is its wavelength? (3 marks) 28. A standing wave with five antinodes is generated in a string. If the waves travel at 17.5m/s with a frequency of 1.40times 10^2 Hz, how long is the string? (3 marks)
- There is an electric field around every electric charge.An electric field exerts a force on electric charges The figure shows two electric fields. The arrows show the direction a positive charge would move in each electric field. Your hair has the positive charge and moves toward the balloon. Comparing electric forces and gravitational forces The force of gravity between you and Earth seems very strong However, at the scale of atoms and molecules electric forces are much stronger than gravitational forces. Electric forces hold electrons and protons together in atoms. The electric force between a proton and an electron in a hydrogen atom is a thousand trillion trillion trillion times larger, or 10^39 times larger, than the gravitational force between the same proton and electron. Electric forces also hold atoms to one another.Electric forces between atoms cause chemical bonds. These electric forces are also much greater than the gravitational forces between the atoms. Deading Essentials - Electricity Get It? 4. Compare the strength of electric forces between protons and electrons 10 the strength of gravitational forces between them. __ __ __
