1 / 22

B3 ENERGY TRANSFERS

(B3). B3 ENERGY TRANSFERS. Year 11 GCSE Physics. LESSON 1 – Efficiency. LEARNING OUTCOMES : Calculate the net energy transfer from a number of different transfers.

ulf
Download Presentation

B3 ENERGY TRANSFERS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. (B3) B3ENERGYTRANSFERS Year 11 GCSE Physics

  2. LESSON 1 – Efficiency • LEARNING OUTCOMES: • Calculate the net energy transfer from a number of different transfers. • Evaluate the efficiencies of energy transfer devices by comparing energy input and useful energy output and use the equation: efficiency = energy output energy input

  3. LESSON 2 – Sensors • LEARNING OUTCOMES: • Appreciate how LDRs and thermistors can be used with electrical circuits to monitor light levels and temperature in a building: • - circuits to include the sensor and a resistor in series • - light and temperature levels monitored via the voltage across the resistor • - how changing the resistor value can affect the voltage across it.

  4. LESSON 3 – Specific Heat Capacity • LEARNING OUTCOMES: • Appreciate that raising the temperature of one kilogram of different materials requires the supply of different quantities of energy and appreciate some of the effects of materials having different specific heat capacities. • Use the equation: change in internal energy (J) = mass (kg) x specific heat capacity (J/kg/C or K) x temperature rise (C or K). • Appreciate and use the relationship between the change in kinetic or potential energy and change in internal energy.

  5. SPECIFIC HEAT CAPACITY

  6. On a HOT DAY at the beach: The sand feels hotter than the sea in the day. BUT… The sand feels cooler than the sea at night. WHY? Both get the same amount of sunlight…

  7. THE REASON IS: Some materials heat up or cool down faster…they are able to take in or give out energy faster than others. We measure this with something called SPECIFIC HEAT CAPACITY.

  8. APPLE PIE… Which cools fastest…filling or crust?

  9. When we heat an object up or cool it down we cause it to gain or lose heat energy:

  10. The SPECIFIC HEAT CAPACITY of a material is: • A measure of how much energy it can hold • The energy needed to raise the temperature by 1ºC. • Different materials have different values of specific heat capacity.

  11. The Specific Heat Capacity essentially measures how much energy 1kg of a material must gain/lose to go up/down in temperature by 1C.

  12. The SPECIFIC HEAT CAPACITY (SHC) of a material can be worked out using the formula: Energy = Mass x SHC x Temperature change For water, SHC = 4200 J/kg/ºC. For aluminium, SHC = 680 J/kg/ºC. Which will heat up/cool down faster?

  13. As a formula with symbols: E = m x c x  Energy change (J) Mass (kg) Specific Heat Capacity for a material (J/kg/C) Temperature difference (C)

  14. EXAMPLE 1: How much energy is needed to heat 2kg of oil up by 25C, if the SHC of the oil is 1000J/kg/ C? SOLUTION: E = mc E = 2 x 1000 x 25 E = 50,000J

  15. EXAMPLE 2: Bartonium has an SHC of 200J/kg/ C. A mass of 3kg is warmed up by a 50W heater switched on for 5 minutes. What is the temperature rise? SOLUTION: E = mc  Pt = mc  50W x 300s = 3kg x 200 x  •  = 15,000 / 600   = 25 C

  16. EXAMPLE 3: How much energy is needed to heat 6kg of water from a temperature of 0 C to 25C , if the SHC of the water is 4200 J/kg/C? SOLUTION: E = mc E = 6 x 4200 x 25 E = 630,000 J

  17. EXPERIMENT: • What is the Specific Heat Capacity (c) of an aluminium block? • How accurate is the experiment? Think about limitations, errors, modifications, etc. Electrical energy (IN): E = V x I x t Heat energy (OUT): E = m x c x 

  18. EXPERIMENT: Why is it poor? • Not all of the heater is inside the block • The heater is not very efficient (only 25% or less?) • The aluminium block is not insulated • Heat does not travel instantly or evenly through the block • Powerpack voltage is not correct (r) • Heater will take time to warm up NB – Our measurements are probably quite precise but for all of the reasons above our answer will not be exact or accurate. Specific Heat Capacity of aluminium = 650 J/kg/C.

  19. LESSON 4 – Resonance • LEARNING OUTCOMES: • Identify situations where resonance is happening: • Recall that all objects vibrate with a natural frequency • Describe how to measure natural frequency of the oscillator. • Know that resonance occurs when an object is subjected to a vibration at its natural frequency. Describe the conditions for resonance in terms of a large amplitude resulting from the driver frequency being equal to the natural frequency of the oscillator. • Appreciate some situations in which resonance is desirable and some in which it is not.

More Related