A row of 15 decorative lights, connected in series, is connected to a power supply. When the supply is switched on, the lights do not work. The owner uses a voltmeter to test the circuit. When the voltmeter is connected across the third bulb in the row of lights, a reading of zero is obtained.
Which of the following cannot be the only fault in the circuit?
A. The filament of the third bulb has broken
B. The fuse in the mains transformer has blown
C.The filament of one of the other bulbs has broken
D.There is a break in the wire from the supply to the transformer
Can someone pls explain how the correct answer is A?
Answers
If the filament of the 3rd bulb is broken, it is essentially an open circuit (no current is flowing) Hence, the voltmeter should read the value of the emf, and should not be zero.
Emf:
Electromotive force (emf) is a measurement of the energy that causes current to flow through a circuit. It can also be defined as the potential difference in charge between two points in a circuit. Electromotive force is also known as voltage, and it is measured in volts.
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Answer:
Because transfer of electricity is independent of filament of . Filament is needed only to light the bulb. Filament heats up when an electric current passes through it, and produces light as a result. The resistance of a lamp increases as the temperature of its filament increases. The current flowing through a filament lamp is not directly proportional to the voltage across it.