O/A Level Physics Simplified

Frequently asked questions and their answers from IGCSE P1
Composed and compiled by Rafquat Sir
Topic: Electricity

Q: Explain how a fuse along with an earth wire provides safety to the user.
A: Earth wires are connected to the metal part of an appliance. When there is a fault in the appliance and a large current flows through the wire, the fuse blows preventing any further flow of current in the circuit.

Q: Explain why electricity is transmitted using high voltages.
A: According to P=VI, since the power remains the same, using high voltage means current can be kept low. Current has a heating effect. Using low current means less energy wasted in the form of heat which in turn increases efficiency.

Q: An appliance requires a current of 4.9A for operating normally. Explain why a fuse rated 5A is not suitable for this appliance.
A: Even a small fluctuation in current will cause the fuse to blow and it has to replaced frequently.

Q: Some appliances have three pin plugs and others have two pin plugs. Explain why?
A: Three pin plugs have an earth connection and are required when the appliance has a metal casing. Appliances with two pin plugs have double insulation. This means that their casings are made from insulating materials such as plastic or rubber. Appliances with a double insulation do not require an earth connection.

Q: Explain why mains electricity is transmitted using AC.
A: Only AC electricity can be stepped up and stepped down.

Q: Explain the advantages of electrostatic painting
A: The paint droplets are given the same charge. Since like charges repel each other, they spread out and cover a wide area. The object being painted is given an opposite charge. Since unlike charges attract each other, the paint droplets stick to the object and reduce wastage

Q: Briefly describe the functions of an electroscope.
A: An UNCHARGED electroscope is used to detect whether an object is charged or uncharged. If a charged object is brought near an electroscope, irrespective of the charge, the electroscope will show a deflection. However, to detect the type of charge on an object, the electroscope must have a known charge. Depending on the type of charge, the deflection of the leaf will either increase or decrease

Q: Briefly describe the advantages and disadvantages of series and parallel circuits.
A: In series, the advantage is less wiring is required to set up a circuit but the disadvantage is that if one component is damaged, the entire circuit is shut down.
In parallel, the advantages are all components connected in parallel can be operated individually and even if one component gets damaged, the entire circuit is not affected.

Q: Explain why a voltmeter has a very high resistance and is always connected in parallel
A: Voltmeters measure the voltage across a component. Since voltage remains same in parallel, they should be connected in parallel.
They must have a very high resistance so that no current flows through them.

P. S conversely you may be asked why an ammeter is always connected in series and has a very low resistance

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