Suppose you walk into a sauna that has an ambient temperature of 50.0C . (a) Calculate the rate of heat transfer to you by radiation given your skin temperature is 37.0C , the emissivity of skin is 0.98, and the surface area of your body is 1.50 m2 . (b) If all other forms of heat transfer are balanced (the net heat transfer is zero), at what rate will your body temperature increase if your mass is 75.0 kg?
TOPIC: ELECTRIC CHARGES Electric Charge There are positive (+) and () charges. o Opposite charges attract (+) o Like charges repel away (++, ) Conserved o Moves around but mount of charge always stays the same o Neutral objects have same amount of positive and negative charges o Charged objects are made up of more of one but still have many of the other Quantized o e=1.60x10 C 19 o Ions are gained net charges by losing or gaining electrons o Conductors and Insulators (more later) Polarization o Polarization can cause neutral objects to be attracted to charged objects Insulators and conductors o This is called induced polarization How can objects be charged if they start as neutral o Conduction Same structured objects (size, shape, mass, etc.) have same charge o Induction Coulomb's Law Between two points (potential energy/at rest), Coulomb's Law states the electric force Coulomb's Law: F = (k|q |1q 2)/r o Q1 and Q2 are charges of the objects. o r=distance, do not confuse with radius o k=constant 8.89x10 Nm /C 2 2 Electric forces are vector and have direction. TOPIC: ELECTRIC FIELDS Electric Fields Vectors They can exist in space where there are not any charged objects F = Eq; charge has a force on it Uniform Fields
