Answer:
- Direct current is a current in which electrons flow in one direction only
- Alternating current is a current in which the direction of the electron flow reverses periodically - so, half a cycle forward, half a cycle backward
There are several advantages of using alternating currents for the transmission of electricity across a country, over large distances. The main advantages are:
- The voltage of alternating currents can be easily increased/decreased by using transformers. For instance, a transformer is used at the beginning of the transmission line to increase the voltage (electricity is transmitted at high voltage in order to reduce dissipated power), and then another transformer is used before the electricity enters the houses, in order to decrease the voltage. Transformers only work with alternating currents.
- It is easy to interrupt the flow of an alternating current, because its value naturally becomes zero every half a cycle, so this is useful in case the current must be interrupted.
False. Radio waves<span> have much longer </span>wavelengths<span> and lower frequencies </span>than<span> </span><span>visible light waves</span>
Pressure is the amount of force per unit area. In formula it
is,
P = F ÷ A
P = 7000 N ÷ 0.4 m2
P = 17,500 N/m2
The amount of pressure the truck exerts on the piston is
17,500 N/m2
The transfer of heat from the Sun is in the form of thermal radiation (also called infrared radiation)
The transfer of heat at the person’s feet is by thermal conduction. During the day the sand will be hot so if you step on it with bare feet there will be conduction of heat to the feet.
