2 A (a) 0.36 W Particles that are 0.2 A 10.8 W heated rise while 15 900 W particles that have Ω 10 000 cooled fall. There must Ω be space between Specific Heat Capacity 7.2 W (p58 59) particles for this to – happen. 4 A Heat is a form of energy. Heat energy travels in Temperature is a measure straight in the form 48 of how hot or cold an of electromagnetic Ω object is. radiation. No particles P = I V are required for heat to P = (V/R) x V 4180 J of heat energy is be transferred by P = V2 / R needed to change the radiation. temperature of 1 kg of (a) 20 W water by 1 °C. Despite having a lower 0.5 W temperature, a cup of 15 V (a) 47 000 J coffee has more heat 6 V 112 750 J energy than a single spark 20 4100 J kg-1 °C-1 from a sparkler. Ω 132.25 270 J kg-1 °C-1 Ω 0.4 kg The tomato has a higher 100 W 5.5 kg specific heat capacity. 7.5 °C More heat energy is 7 V 4 °C required to change its temperature. 66 752 400 J Ω Fire fighting clothing is (a) 407 380 J kg-1 °C-1 made of a substance that is Ω 0.57 fire resistant and a poor Ω 11 232 000 J 2.5 °C conductor of heat. The clothing is insulated (a) Electrical Heat 12 kg trapped air which S1 and S2 prevents heat transfer 4.6 A (a) 618 J kg-1 °C-1 from surroundings. 1058 W The experimental value Reflective panels are used 37.5 is larger. This is because for visibility but also Ω 1411 W not all heat energy is reflect heat radiation. 63 480 + 677 280 = absorbed by the copper 740 760 J block. Conduction: a fabric insulating cover on the High current in Heat Transfer (p60) outside of the boiler transmission lines results in prevents heat loss. high energy loss. Using (a) Heat energy is Convection: The top of the high voltages reduces the transferred by boiler is air-tight to prevent current in transmission vibrations of particles heat loss. lines and therefore reduces that are in contact with Radiation: The interior (or energy loss. each other. exterior) of the boiler can be coated with a reflective
2 A 0.2 A 15 Ω 10 000 Ω 7.2 W 4 A 48 Ω 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-1 °C-1 270 J kg-1 °C-1 0.4 kg 5.5 kg 7.5 °C 4 °C 752 400 J 380 J kg-1 °C-1 2.5 °C 12 kg (a) 618 J kg-1 °C-1 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 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 trapped air which prevents heat transfer from surroundings. Reflective panels are used for 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
Electricity-and-Energy-Problem-Booklet-sbu8z8.docx