Sound, Waves and Electricity
Question 1
A. As a sound wave through a uniform medium, the wave will experience a gradual reduction in its
1. Power
As a sound wave travels through a uniform medium, the amount of energy transmitted into the medium gradually diminishes. This energy which is also the power of the sound wave too diminishes gradually because amplitude in a sound wave is a maximum which diminishes gradually. The speed and frequency of a sound wave travelling through a uniform medium remains constant as the speed and frequency of sound waves are determined by the properties of the medium and not of the wave itself.
B. As sound moves through matter, at each compression zone there is a localized region of increased
2. Pressure
A compression zone of a sound wave is one in which the sound wave is travelling through the medium with high pressure. In a sine curve, the peak points on the graph would represent a compression zone. Due to fluctuations in the pressure of a sound wave, a sound wave is also known as a pressure wave.
Question 2
The patient is partially undressed for examination in a room at low temperature due to which the body temperature of the body drops. This happens when the temperatures of the two matters namely solid (patient’s body) and gas (air in the room) is trying to become uniform. The cold air in the room tries to make the temperature uniform by cooling the patient’s body especially in the areas not clothed. This causes a drop in the patient’s body temperature, significantly in the unclothed areas exposed to the cold air. The clothed region of the patient’s body is providing thermal insulation to the patient by creating a barrier between the warm body temperature and the cold air in the room. This barrier minimizes heat loss in clothed areas and the unclothed areas suffer greater heat loss.
Question 3
A. The electric blanket consists of heating coils wound in a serpentine fashion inside a thick insulating blanket which provides heat when current heats up the coil. Electric shocks are prevented in the electric blanket by using insulation around the heating coils and by using a thick blanket which provides protection from electric shocks. Auto-shutoff facility of the blanket is also a vital function which protects the heating coil from overheating of the coil which may result in a short circuit.
B. Though electric shock can be minimized in the above mentioned ways, electric shocks cannot be eliminated in electric blankets. Safe handling of the blanket is a must to prevent damage to the coils, failing which can cause electric shocks. Overusing, washing and spilling wet substances in the blanket can all cause an electric shock.
Question 4
Given: Power, P = 50W, Standard power point voltage, V = 120V.
P = V * I
Thus, I = P / V = 50 / 120 = 0.416A
According to Ohm’s Law,
V = I * R, where R is the resistance offered by the circuit.
Thus, R = V / I = 120 / 0.416 = 288Ω
Resistance offered by the electric blanket = 288Ω
References
World Wide Web Page
Basics of Waves Review, [Online], Available:
http://www.physicsclassroom.com/reviews/waves/wavesans1.cfm
[3 May 2016].
World Wide Web Page
Chapter 10: The Nature of Waves, [Online], Available:
http://www.boomeria.org/physicstextbook/ch10.html
[2 May 2016].
World Wide Web Page
Heated Mattress Pads and Electric Blankets: How Do They Really Work?, [Online], Available:
http://www.electricblanketinstitute.com
[2 May 2016].
World Wide Web Page
Kurtus, R. (2014) Thermal Insulation, [Online], Available:
http://www.school-for-champions.com/science/thermal_insulation.htm#.VyhOPj-rZ1l
[3 May 2016].
World Wide Web Page
Sound is a Pressure Wave, [Online], Available:
http://www.physicsclassroom.com/class/sound/Lesson-1/Sound-is-a-Pressure-Wave
[2May 2016].
