P = I V Temperature is a measure form of P = (V/R) x V of how hot or cold an electromagnetic P = V2 / R object is. radiation. No particles are required for heat to 20 W 4180 J of heat energy be transferred by (a) 0.5 W is needed to change the radiation. 15 V temperature of 1 kg of 6 V water by 1 °C. Despite having a 20 lower temperature, a cup Ω 132.25 (a) 47 000 J of coffee has more heat Ω 112 750 J energy than a single spark 100 W 4100 J / kg °C from a sparkler. 270 J / kg °C 7 V 0.4 kg The tomato has a 5.5 kg higher specific heat 66 7.5 °C capacity. More heat energy Ω 4 °C is required to change its (a) 407 temperature. Ω 0.57 752 400 J Ω 11 232 000 J Fire fighting clothing 380 J / kg °C is made of a substance that (a) Electrical Heat is fire resistant and a poor S1 and S2 2.5 °C conductor of heat. 4.6 A The clothing is insulated 1058 W 12 kg using trapped air which 37.5 prevents heat transfer Ω 1411 W (a) 618 J / kg °C from surroundings. 63 480 + 677 280 = The experimental Reflective panels are used 740 760 J value is larger. This is for added visibility but also because not all heat reflect heat radiation. High current in energy is absorbed by transmission lines results in the copper block. Conduction: a fabric high energy loss. Using insulating cover on the high voltages reduces the Heat Transfer (p60) outside of the boiler current in transmission prevents heat loss. lines and therefore reduces (a) Heat energy is Convection: The top of the energy loss. transferred by boiler is air-tight to prevent vibrations of particles heat loss. (a) 0.36 W that are in contact with Radiation: The interior (or 10.8 W each other. exterior) of the boiler can 900 W Particles that are be coated with a reflective heated rise while material (such as foil) to Specific Heat Capacity particles that have prevent heat loss. (p58 59) cooled fall. There must – be space between Pressure (p61 62) – Heat is a form of particles for this to energy. happen. Pressure is the force Heat energy travels in applied to an area of a straight lines in the surface.
P = I V P = (V/R) x V P = V2 / R (a) 20 W 0.5 W 15 V 6 V 20 Ω 132.25 Ω 100 W 7 V 66 Ω (a) 407 Ω 0.57 Ω 11 232 000 J (a) Electrical Heat S1 and S2 4.6 A 1058 W 37.5 Ω 1411 W 63 480 + 677 280 = 740 760 J High current in transmission lines results in high energy loss. Using high voltages reduces the current in transmission lines and therefore reduces energy loss. (a) 0.36 W 10.8 W 900 W Specific Heat Capacity (p58 – 59) Heat is a form of energy. Temperature is a measure of how hot or cold an object is. 4180 J of heat energy is needed to change the temperature of 1 kg of water by 1 °C. (a) 47 000 J 112 750 J 4100 J / kg °C 270 J / kg °C 0.4 kg 5.5 kg 7.5 °C 4 °C 752 400 J 380 J / kg °C 2.5 °C 12 kg (a) 618 J / kg °C The experimental value is larger. This is because not all heat energy is absorbed by the copper block. Heat Transfer (p60) (a) Heat energy is transferred by vibrations of particles that are in contact with each other. Particles that are heated rise while particles that have cooled fall. There must be space between particles for this to happen. Heat energy travels in straight lines in the form of electromagnetic radiation. No particles are required for heat to be transferred by radiation. Despite having a lower temperature, a cup of coffee has more heat energy than a single spark from a sparkler. The tomato has a higher specific heat capacity. More heat energy is required to change its temperature. Fire fighting clothing is made of a substance that is fire resistant and a poor conductor of heat. The clothing is insulated using trapped air which prevents heat transfer from surroundings. Reflective panels are used for added visibility but also reflect heat radiation. Conduction: a fabric insulating cover on the outside of the boiler prevents heat loss. Convection: The top of the boiler is air-tight to prevent heat loss. Radiation: The interior (or exterior) of the boiler can be coated with a reflective material (such as foil) to prevent heat loss. Pressure (p61 – 62) Pressure is the force applied to an area of a surface.
Electricity-and-Energy-Problem-Booklet-St-Lukes.docx