Railway · Police · Defence
Which instrument is used to measure the electric current in a circuit?
Answer (Detailed Solution Below)View answer ▾Hide ▴
Answer: Option A — Ammeter
Detailed Solution
An ammeter is an instrument used to measure the electric current flowing through a circuit. Current is measured in amperes (symbol A), named after the French physicist André-Marie Ampère, which is how the ammeter gets its name. One ampere is the flow of one coulomb of charge per second.
An ammeter is always connected in series with the component through which the current is to be measured, so that the same current flows through both. An ideal ammeter has zero resistance, so that it does not change the current in the circuit. Real ammeters have a very low resistance. In practice, an ammeter is made by connecting a low resistance, called a shunt, in parallel with a galvanometer. The shunt carries most of the current, protecting the sensitive galvanometer.
If an ammeter is wrongly connected in parallel, a very large current will flow through it because of its low resistance, which can damage the instrument.
Related instruments:
Voltmeter: measures the potential difference (voltage) between two points, in volts. It is always connected in parallel with the component. An ideal voltmeter has infinite resistance; it is made by connecting a high resistance in series with a galvanometer.
Galvanometer: detects small currents and shows their direction.
Ohmmeter: measures resistance, in ohms.
Multimeter: a single instrument that can measure current, voltage and resistance.
Ohm's law, given by Georg Simon Ohm, states that the current through a conductor is directly proportional to the potential difference across it, at constant temperature: V = IR, where R is the resistance.
Why not the other options?
- ✗A voltmeter measures potential difference and is connected in parallel.
- ✗An ohmmeter measures resistance.
- ✗A potentiometer measures the emf of a cell and compares potential differences accurately.
Quick tip
Remember: Ammeter = current, in series, very low resistance (shunt in parallel with galvanometer); voltmeter = voltage, in parallel, very high resistance.
💬 Discussions on this question
Ask a doubt ›Still stuck on this question? Ask our faculty and fellow students — answers appear here.
Ask a doubtMore Electricity & Magnetism Questions
View all ›- Q1.A freely suspended bar magnet always comes to rest in which direction?
- Q2.The process of depositing a layer of a desired metal on another material by means of electricity is called:
- Q3.Which instrument is used to detect the presence of an electric current in a circuit?
- Q4.Which rule is used to find the direction of the magnetic field around a straight current-carrying conductor?
More General Knowledge Questions
- Q1.The techniques of Rasa and Bhava used in Indian classical dance trace their origin to which ancient text?Indian Dance Forms
- Q2.Lavani, Powada, Koli, Waghya Murali and Dhangari Gaja are folk dances of which state?Indian Dance Forms
- Q3.The one-act play associated with the Sattriya tradition of Assam is called:Indian Dance Forms
- Q4.Which dance form of Goa is known as the 'Warrior Dance'?Indian Dance Forms
- Q5.Manipuri dance is based on the Rasleela themes of:Indian Dance Forms
Electricity & Magnetism — Preparation
This question tests your understanding of Electricity & Magnetism, a key topic in the General Knowledge section. The detailed solution above uses a step-by-step approach to show the reasoning, and where available, a shortcut that helps you solve similar questions in under 90 seconds during the actual exam.
This topic covers electric charge, current, voltage and resistance, Ohm's law, series and parallel circuits, electric power and energy, the heating effect of current, magnets and magnetic fields, electromagnetic induction, and devices such as motors, generators, transformers and fuses. Questions commonly ask about units (the ampere, volt, ohm and kilowatt-hour), why household appliances are connected in parallel, what a fuse is made of and why, and which device converts mechanical energy into electrical energy (a generator). Remember that a transformer works only with alternating current. Practise the electricity and magnetism questions below, written in the style of the general awareness sections of exams such as SSC, banking, railways, CUET GAT, MAH CET and CLAT. Each question comes with a detailed explanation that adds related facts, so every question helps you revise more than one point.