Force, Energy & Communication
Lesson 5
Lesson Objectives
To consolidate our knowledge on electrical power from last lesson To look at the costing for electricity
To investigate the magnetic effect of a current
REMEMBER!
Charge passed (coulombs) = Current X (amperes) Time (seconds)
Q = It
Electrical power (watts)
=
Current (amps)
X
Voltage (volts)
P = IV
Cost of Electricity
cost of electricity = power (kW) x time (h) x cost of 1kWh
Copy and complete this table
Appliance Rating (kW)
Storage heater
Cooker 1-bar electric fire Kettle Iron
Time (h) Energy (kWh)
4
2 1.5 0.1 1.2
Cost at 10p per unit
8 x 10 = 80p
2
7 1 2 1
2x4=8
„Fridge Lamp CD player
0.12 0.06 0.012
24.0 6.0 2.0
Copy and complete this table
Appliance Rating (kW)
Storage heater
Cooker 1-bar electric fire Kettle Iron
Time (h) Energy (kWh)
4
2 1.5 0.1 1.2
Cost at 10p per unit
8 x 10 = 80p
14x10 = 140p 1.5 x 10 = 15p 0.2 x 10 = 2p 1.2 x 10 = 12p
2
7 1 2 1
2x4=8
7x2 = 14 1x1.5 = 1.5 2x0.1 = 0.2 1 x 1.2 = 1.2
„Fridge Lamp CD player
0.12 0.06 0.012
24.0 6.0 2.0
0.12x24 = 2.88 0.06x6.0= 0.36
0.012x2= 0.024
2.88 x 10 = 28p 0.36 x 10 = 3.6p
0.024 x 10 = 0.24p
Copy and complete the following summary using these words
joules energy twice energy voltage previous subtract
To find the number of units used on an electricity bill, ………….. the …………… meter reading from the present one. You pay for the …………. you have used not the ………….. or the current supplied. If a label on an appliance says “1kWh” it means it will use ………….. at the rate of 1000 …………… per second . A “2kW” appliance uses energy …………….. as quickly as a “1kW” appliance.
Electromagnetic induction
The magnetic force on a current
When a current flows through a wire held between two poles of a magnet there is an upwards force on it.
The magnetic force on a current
The force becomes stronger if… the current is increased
a stronger magnet is used there is a greater length of wire in the magnetic field
The magnetic force on a current
The force isn‟t always upwards . It depends on the current and the field directions. If the wire is in line with the field, there isn‟t any force at all.
Lesson Objectives
To consolidate our knowledge on electrical power from last lesson To look at the costing for electricity
To investigate the magnetic effect of a current