Ass. Chapter 4 - Physics Past Paper PDF

# Ass. (CHAPTER 4) ## Define the following: - **Heat:** - **Temperature:** - **Zeroth law of thermodynamics:** - **Absolute zero:** - **1kcal:** - **The British thermal unit (BTU):** - **Heat capacity C:** - **Specific heat capacity:** - **Power** - **Latent heat** ## Complete 1. There are th...

# Ass. (CHAPTER 4) ## Define the following: - **Heat:** - **Temperature:** - **Zeroth law of thermodynamics:** - **Absolute zero:** - **1kcal:** - **The British thermal unit (BTU):** - **Heat capacity C:** - **Specific heat capacity:** - **Power** - **Latent heat** ## Complete 1. There are three different mechanisms of heat transfer, which are - ... - ... - ... 2. The amount of heat required to change the phase of 1 kg of a substance from solid to liquid without change in temperature is called ... 3. The heat capacity depends on ... and ... 4. The heat capacity is always ... ## Choose the right answer **(1)** The kinetic energy is always - (a) positive - (b) negative - (c) zero **(2)** Sea breeze is an application of - (a) conduction - (b) convection - (c) radiation **(3)** The unit of the radiated power is - (a) Joule (J) - (b) Newton (N) - (c) Watt (W) **(4)** If the force has no component in the direction of motion, then the work is ... - (a) positive - (b) negative - (c) zero **(5)** If the heat is removed from the system, then the sign of Q is... - (a) positive - (b) negative - (c) zero **(6)** If Q is positive then heat is ...... the system - (a) added to - (b) removed from - (c) stable in **(7)** The vacuum in the thermos bottle is used to prevent the transfer of heat by - (a) conduction - (b) convection - (c) both **(8)** The counter-current exchange is an example of transfer of heat by - (a) conduction - (b) convection - (c) radiation **(9)** The mechanical advantage of the second class lever is always - (a) greater than one - (b) less than one - (c) either larger or smaller than one **(10)** If the temperature is 86 °F, the corresponding temperature in °C is - (a) 30 °C - (b) 68 °C - (c) 86 °C **(12)** Heat is the ... transferred from hot objects to cold objects - (a) force - (b) power - (c) energy **(13)** One kcal is the amount of heat needed to increase the temperature of 1kg of water - (a) one degree °C - (b) from 14.5 °C to 15.5 °C - (c) from 63 0F to 64 °F **(14)** The unit of the latent heat is - (a) J/kg - (b) J/K or J/°C - (c) J/kg °C or J/kg.K **(15)** The unit of the heat capacity is - (a) J/kg - (b) J/K or J/°C - (c) J/kg °C or J/kg.K **(17)** The unit of the specific heat capacity is ... - (a) J/kg - (b) J/K or J/°C - (c) J/kg °C or J/kg.K **(18)** The heat capacity C is always .... - (a) positive - (b) negative - (c) zero **(19)** The silver film in the thermos bottle prevents loss of heat by - (a) conduction - (b) convection - (c) radiation **(20)** The heat transferred by conduction is ... proportional to the hot area - (a) directly - (b) inversely - (c) not **(21)** The perfect reflector has emissivity e equal to - (a) one - (b) zero - (c) between 1 and 0 **(22)** All objects have emissivity ... - (a) one - (b) zero - (c) between 1 and 0 **(24)** The heat capacity C depends on the ... of the substance - (a) type - (b) mass (m) - (c) a and b **(23)** The black body has emissivity e - (a) = one - (b) = zero - (c) between 1 and 0 **(25)** The specific heat capacity c depends on the ... of the substance - (a) type - (b) mass (m) - (c) a and b **(26)** The lowest temperature below which it's impossible to cool any object is the ... - (a) specific heat capacity - (b) absolute zero - (c) heat capacity **(27)** The amount of heat Q needed to raise of temperature of the substance one degree Celsius is called - (a) specific heat capacity - (b) absolute zero - (c) heat capacity **(29)** If Q is the amount of heat given to the substance of mass m causing rise of temperature T then the heat capacity is given by - (a) C = Q . m - (b) C = Q/AT - (c) C = m/Q **(30)** The amount of heat Q needed to raise of temperature of 1kg substance one degree Celsius is called ... - (a) heat capacity - (b) specific heat capacity - (c) absolute zero **(31)** ... is the amount of heat needed to increase the temperature of 1kg of water, from 14.5 °C to 15.5 °C - (a) 1 kcal - (b) specific heat - (c) heat capacity **(32)** The mechanism that decreases the heat loss from the cold limbs is called - (a) direct current exchange - (b) inter-current exchange - (c) countercurrent exchange **(33)** An object with large heat capacity requires a ... amount of heat for each increment in temperature - (a) large - (b) small - (c) same **(34)** The rate change of the internal energy is called - (a) kinetic energy - (b) potential energy - (c) metabolic rate # On New Year's Day, several human “polar bears" prepare for their annual dip into the icy waters of Narragansett Bay. One of these hardy souls has a surface area of 1.15 m² and a surface temperature of 303 K (~30 °C). Find the net radiated power from this person (a) in a dressing room, where the temperature is 293 K (~20 °C) and (b) outside, where the temperature is 273 K (~0 °C). Assume an emissivity of 0.900 for the person's skin. # | SOLUTION # # 2- Lowest Temperature on Earth The official record for the lowest temperature ever recorded on Earth was set at Vostok, Antarctica, on July 21, 1983. The temperature on that day fell to -89.9 °C, well below the temperature of dry ice. What is this temperature in degrees Fahrenheit? # 3- The temperature at the surface of the Sun is about 6000 К. Convert this temperature to the (a)Celsius and (b)Fahrenheit scales. # 4- One day you notice that the outside temperature increased by 27 F° between your early morning jog and your lunch at noon. What is the corresponding change in temperature in the (a) Celsius and (b) Kelvin scales? # 5- Calculate the radiated power from a sphere with a radius of 2 cm at the temperature 300 K. Assume the emissivity is unity.