Get premium membership and access questions with answers, video lessons as well as revision papers.
- A house has five rooms each with a 60 W, 240 V bulb. If the bulbs are switched on from 7.00 pm to 10.30 pm,...(Solved)
A house has five rooms each with a 60 W, 240 V bulb. If the bulbs are switched on from 7.00 pm to 10.30 pm, calculate the;
(a) Power consumed per day in kWh
(b) Cost per week for lighting those rooms if it costs 90 cents per unit.
Date posted: October 16, 2018. Answers (1)
- An electric heater is made of a wire of resistance 100 ${\Omega}$ connected to a 240 V mains supply. Determine the; (a) Power rating of...(Solved)
An electric heater is made of a wire of resistance 100 ${\Omega}$ connected to a 240 V mains supply. Determine the;
(a) Power rating of the heater
(b) Current flowing in the circuit
(c) Time taken for the heater to raise the temperature of 200 g of water from 23oC to 95oC. (specific heat capacity of water = 4,200 J Kg-1K-1)
(d) Cost of using the heater for two hours a day for 30 days if the power company charges Ksh 5.00 per kWh.
Date posted: October 16, 2018. Answers (1)
- An electric kettle is rated at 2,500 W and uses a voltage of 240 V. (a) If electricity costs Ksh 1.10 per kWh, what is...(Solved)
An electric kettle is rated at 2,500 W and uses a voltage of 240 V. (a) If electricity costs Ksh 1.10 per kWh, what is the cost of running it for 6 hrs? (b) What would be its rate of dissipating energy if the mains voltage was dropped to 120 V?
Date posted: October 16, 2018. Answers (1)
- An electric heater running on 240 V mains has a current of 2.5 A. (a) What is its power rating? (b) What is the resistance...(Solved)
An electric heater running on 240 V mains has a current of 2.5 A. (a) What is its power rating? (b) What is the resistance of its element?
Date posted: October 16, 2018. Answers (1)
- What are the dangers of high voltage transmission lines?(Solved)
What are the dangers of high voltage transmission lines?
Date posted: October 16, 2018. Answers (1)
- What is electricity distribution?(Solved)
What is electricity distribution?
Date posted: October 16, 2018. Answers (1)
- Briefly explain the process of power generation and transmission(Solved)
Explain the process of power transmission
Date posted: October 16, 2018. Answers (1)
- What is power transmission?(Solved)
What is power transmission?
Date posted: October 16, 2018. Answers (1)
- Outline uses of transformers(Solved)
Outline uses of transformers.
Date posted: October 16, 2018. Answers (1)
- A step-up transformer has 10,000 turns in the secondary coil and 100 turns in the primary coil. An alternating current of 0.5 A flows in...(Solved)
A step-up transformer has 10,000 turns in the secondary coil and 100 turns in the primary coil. An alternating current of 0.5 A flows in the primary circuit when connected to a 12.0 V a.c. supply.
(a) Calculate the voltage across the secondary coil (b) If the transformer has an efficiency of 90%, what is the current in the secondary coil?
Date posted: October 16, 2018. Answers (1)
- A current of 0.6 A is passed through a step up transformer with a primary coil of 200 turns and a current of 0.1 A...(Solved)
A current of 0.6 A is passed through a step up transformer with a primary coil of 200 turns and a current of 0.1 A is obtained in the secondary coil. Determine the number of turns in the secondary coil and the voltage across if the primary coil is connected to a 240 V mains.
Date posted: October 16, 2018. Answers (1)
- What are the applications of mutual induction?(Solved)
What are the applications of mutual induction?
Date posted: October 16, 2018. Answers (1)
- How does mutual induction occur?(Solved)
How does mutual induction occur?
Date posted: October 16, 2018. Answers (1)
- Factors affecting the magnitude of the induced induced electromagnetic force (e.m.f)(Solved)
Factors affecting the magnitude of the induced induced electromagnetic force (e.m.f)
Date posted: October 16, 2018. Answers (1)
- Describe an experiment to show that e.m.f is induced due to the relative motion of the wire or the magnet. (Solved)
Describe an experiment on electromagnetic induction to show that e.m.f is induced due to the relative motion of the wire or the magnet.
Date posted: October 16, 2018. Answers (1)
- Explain unique properties of electromagnetic waves(Solved)
Explain unique properties of electromagnetic waves.
Date posted: October 16, 2018. Answers (1)
- A VHF radio transmitter broadcasts radio waves at a frequency of 30 M Hz. What is their wavelength?(Solved)
A VHF radio transmitter broadcasts radio waves at a frequency of 30 M Hz. What is their wavelength?
Date posted: October 16, 2018. Answers (1)
- What is electromagnetic spectrum?(Solved)
What is electromagnetic spectrum?
Date posted: October 16, 2018. Answers (1)
- A material of density 8.5 gcm-3 is attached to a piece of wood of mass 100g and density 0.2 gcm-3. Calculate the volume of material...(Solved)
A material of density 8.5 gcm-3 is attached to a piece of wood of mass 100g and density 0.2 gcm-3. Calculate the volume of material X which must be attached to the piece of wood so that the two just submerge beneath a liquid of density 1.2 gcm-3.
Date posted: October 16, 2018. Answers (1)
- A balloon made up of a fabric weighing 80 N has a volume of 1.0 × 107 cm. the balloon is filled with hydrogen of...(Solved)
A balloon made up of a fabric weighing 80 N has a volume of 1.0 × 107 cm. the balloon is filled with hydrogen of density 0.9 kgm-3. Calculate the greatest weight in addition to that of the hydrogen and the fabric, which the balloon can carry in air of average density 1.25 kgm-3
Date posted: October 16, 2018. Answers (1)