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Electricity Can you fill in the symbols for the circuit components using page 176 and 181.

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Presentation on theme: "Electricity Can you fill in the symbols for the circuit components using page 176 and 181."— Presentation transcript:

1 Electricity Can you fill in the symbols for the circuit components using page 176 and 181

2 Todays lesson Electrical symbols Charge Series and Parallel circuits Understand that current is the rate of flow of charge Recall and use: Q = It Looking at current in different circuits Conventional current

3

4 cell energy electron lamp

5 cell energy electron lamp Can you copy this please?

6 Electrons Hi, Im Eleanor the electron.

7 Coulomb of charge (electrons) Think of it as a bag of electrons (containing electrons!)

8 Current The number of Coulombs flowing past a point in the circuit every second. I = Q/t A Im counting how many coulombs of electrons go past me every second 1 Amp = 1 coulomb per second

9 Current The number of Coulombs flowing past a point in the circuit every second. I = Q/t A Im counting how many coulombs of electrons go past me every second 1 Amp = 1 coulomb per second Can you copy this please?

10 Lets build some circuits! Do experiments 31.4 to page

11 In a series circuit Current is the same at any point in the circuit 2.5 A

12 In a series circuit Current is the same at any point in the circuit 2.5 A Can you copy this please?

13 Todays lesson Looking at current in different circuits Recall and use: Q = It Understand that voltage is the number of joules per coulomb transferred Looking at voltage in different circuits

14 In a parallel circuit The current splits (total current stays the same) 2.5 A 1.25 A

15 In a parallel circuit The current splits (total current stays the same) 2.5 A 1.25 A Can you copy this please?

16 Milliamps! 1 A = 1000 mA 1 mA = ?

17 Milliamps! 1 A = 1000 mA 1 mA = A

18 Stand up!

19 Voltage(emf) V Im checking the difference in energy (per coulomb) between the 2 red arrows 1 Volt = 1 Joule per coulomb

20 Voltage (p.d.) V Im checking the difference in energy (per coulomb) before and after the lamp 1 Volt = 1 Joule per coulomb

21 Voltage Voltage is the amount of energy transferred (changed) per coulomb of charge.

22 Lets build some circuits!

23 Stand up!

24 In a series circuit The sum of the voltages across the lamps equals the voltage across the cells 9 V 3 V

25 In a series circuit The sum of the voltages across the lamps equals the voltage across the cells 9 V 3 V Can you copy this please?

26 Stand up!

27 In a parallel circuit In a simple parallel circuit, voltage across each lamp equals the voltage across the cells 5 V

28 In a parallel circuit In a simple parallel circuit, voltage across each lamp equals the voltage across the cells 5 V Can you copy this please?

29 Todays lesson Understand the term resistance Recall and use: V =IR

30 Stand up!

31 Resistance Measures how difficult it is for current to flow. Measured in Ohms (Ω) VA Resistance = voltage/currentR = V/I

32 Resistance Measures how difficult it is for current to flow. Measured in Ohms (Ω) VA Resistance = voltage/currentR = V/I Can you copy this please?

33 Ohms Law V = IR V R I X

34 Lets measure a resistance!

35 Resistance of a lamp AV Resistance = voltage/currentR = V/I Vary the voltage and current using a variable resistor (rheostat). Plot a graph of resistance against current

36 Resistance of a lamp V(V)I(A)R(Ω) I(A) R(Ω)

37 Homework! Read pages 176 and 177 Answer questions on page 177 Due Wednesday 25 th November

38 Resistance of a lamp As the current in a lamp increases, it gets hotter, and its resistance increases. Why?

39 Resistance of a lamp As the current in a lamp increases, it gets hotter, and its resistance increases. Copy please.

40 Lets try some resistance questions

41 Todays lesson Understand the term power Recall and use: P =VI Recall and use E = VIt

42 Power The amount of energy used by a device per second, measured in Watts (Joules per second) VA Power = voltage x currentP = VI

43 Power The amount of energy used by a device per second, measured in Watts (Joules per second) VA Power = voltage x currentP = VI Can you copy this please?

44 Power of a lamp AV Power = voltage x currentP = VI Measure the power of the lamp at its operating voltage. What is the electrical energy being turned into?

45 Example A 200 W television is plugged into the 110V mains. What is the current in the television? P I V X

46 Example A 200 W television is plugged into the 110V mains. What is the current in the television? I = P/V = 200/110 = 1.8A P I V X

47 Example A kettle uses 240V and 8A. What is its power? P I V X

48 Example A kettle uses 240V and 8A. What is its power? P = VI = 240x8 = 1920W (=1.9kW) P I V X

49 Remember Power is the amount of energy used by a device per second, measured in Watts (Joules per second) VA Power = voltage x currentP = VI

50 Total energy So the total energy transformed by a lamp is the power (J/s) times the time the lamp is on for in seconds, E = VIt E = energy transformed (J) V = Voltage (also called p.d.) I = current (A) t = time (s)

51 Example A kettle uses 240V and 8A. What is its power? P = VI = 240x8 = 1920W (=1.9kW) How much energy does the kettle use in 5 minutes? P I V X

52 Example A kettle uses 240V and 8A. What is its power? P = VI = 240x8 = 1920W (=1.9kW) How much energy does the kettle use in 5 minutes? E = VIt = 240x8x300 = J P I V X

53 Simple!

54 Lets try some questions!


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