Electricity calculations

 1.         Copy and complete this table: 

 2.         If a resistor has a resistance of 200ohms calculate the voltage required to cause a current of 100mA to flow

 3.         Repeat for a resistance of 200lohms and a current of 20Amperes

 4.         A 300kohm resistor has 1A flowing through it.  What is the p.d. across it?

  5.                                                                               

(a)        Write down the current flowing through R₁

(b)        Calculate the resistance of R₁

(c)        Calculate the p.d. across R₂

(d)        Calculate the resistance of R₂

(e)        Write down all the scientific principles that this question relies upon.

 6.         What is the power of an appliance that passes 200J of energy in 4 seconds

 7.         What is the power of an electric iron that passes 600kJ in 14 minutes?

 8.         What is the power of an electric kettle that uses mains electricity passes a current of 3A?

 9.         A fluorescent light bulb passes a current of 150mA when connected to the mains.  What is its power rating?

10.        What is the current passed through a colour tv rated at 340W that is connected to the mains?

11.        Why would it be wrong to use a 5A fuse in an immersion heater rated at 3000W (connected to the mains)?

12.        Why would it be wrong to use a 13A fuse in a table lamp rated at 60W when connected to the mains supply?

13.       A 3kW electric fire is used for 10 minutes.  (a) Calculate the Joules of electricity that it converts.  (b) What energy is the electricity converted into?

** 14.    What is the resistance of a mains powered electric fire rated at 1kW?

** 15.    An electric light bulb, rated at 100W, has a resistance of 26 ohms.   Calculate the voltage of the power supply.

16.       A dishwasher has a resistance of 19 ohms.  Calculate the energy converted by the dishwasher during a half hour cycle if used at mains voltage?

17.       Calculate the kWhours of electricity consumed by a 2kW electric fire in 2 hours.

18.       If 1 unit of electricity costs 7p (1kWhr = 7p) calculate the cost of using an immersion heater rated at 4000W for 10hours.

** 19.    Calculate the resistance of an electric kettle if it costs 16.8p per hour to run it on mains power. (Take 1 unit = 7p)

20.       An office has five 60W bulbs, a 2kW electric fire and a 200W computer.  Calculate the maximum electricity costs of  this office per 24 hours period.  (Take 1 unit = 7p)