# Practice questions

Well this took me quite some time but I hope it helps,

It is just some summary, exam and how science work questions. try them and see what you get . Post your mark here as soon as I get the answers up. I need a break :D

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Physics revision questions. Mains electricity.
Summary questions:
1. In a mains circuit which wire:
a. Is earthed at the local substation?
b. Alternates in potential?
2. An oscilloscope is used to display the potential difference of an alternating voltage supply current.
How would the trace change if:
a. The potential difference is increased?
b. The frequency is increased?
3. Complete `a.' and `b.' using words below:
Earth Live Neutral
a. When a mains appliance is switched on, current passes through it via the ____________ and the
___________ wire.
b. In a mains circuit:
i. The _____________ wire is blue,
ii. The _____________ wire is brown,
iii. The _____________ wire is green and yellow.
4. Complete the sentences:
a. Wall sockets are connected in _________ with each other.
b. A fuse in the mains plug is in ________ with the appliance and cuts off the _____ wire if too much
current passes through the appliance.
5.
a. Calculate the current in a 230 V, 2.5kW electric kettle.
b. Which fuse 3A, 5A, and 13A would you fit in the kettle plug?
c. Calculate the power supplied to a 230V electric toaster when the current through it is 4A.
6. [Higher] Calculate the charge flow through a resistor when the current is 6A for 200s.
7. [Higher] A 5 Ohms resistor is in series with a lamp, a switch and a 12 V battery.
a. Draw the circuit diagram.
b. When the switch is closed for 60 seconds, a direct current of 0.6A passes through the resistor.
Calculate:
i. The energy supplied by the battery.
ii. The energy transformed in the resistor.
iii. The energy transformed in the lamp.
Exam style questions:
1. An electric heater is connected to a 230V mains supply. The current flowing through the heater is
12A.

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Physics revision questions. Mains electricity.
a. What is the power of the heater? (2 marks)
b. The heater is switched on for 30 minutes. Calculate how much charge flows through the heater
during this time and give the unit.
2. State and explain why parts of the plug are made out of:
i. Plastic
ii. Brass
3. Explain:
a. Why appliances with metal cases need to be earthed but appliances with metal cases don't?
b. Which wire in a circuit should contain the fuse?