Types of Balance
10 Minutes
Types of balances for students explains beam balances, physical balances, spring balances, and digital scales. A science lesson in English.
- Beam balance (tarasu) and measuring with reference weights
- Physical balance kept in a glass box to measure 10 mg to 200 g
- Spring balances using Hooke's law and precise digital balances
What this lesson teaches
A balance is an instrument used to measure the mass or weight of an object by comparing it to a reference weight or by measuring the force of gravity acting on it. Different balances are chosen based on the size of the object, ranging from heavy transport containers to tiny milligrams of medicine.
Common balance and physical balance
- A common balance, also called a beam balance (tarasu), compares an object against a reference weight to measure amounts from 5 grams up to 5 kilograms.
- A balance must be light enough for its purpose, because a heavy scale pan will not even register a light object like a 150-gram phone.
- A physical balance (iyarpial tarasu) is kept inside a closed glass box so that wind and gentle breezes do not cause the pans to sway and create errors.
- Jewelers and pawn shops use physical balances to weigh precious items like gold and diamonds from 10 milligrams up to 200 grams, moving in steps of 10 milligrams.
Spring balance and Hooke's law
A spring balance measures weight without needing any reference weights by using the pull of Earth's gravity. It operates on Hooke's law, which explains that an elastic spring elongates when a load or pulling force is applied to it. For instance, if a 10-gram load stretches the spring by 1 centimeter, a 20-gram load stretches it by 2 centimeters, allowing the weight to be read from the stretch. Because it relies entirely on local gravity, a spring balance will show different readings on the Moon or Mars compared to Earth.
Uses of spring balances
Large spring balances can be attached directly to cranes to weigh heavy cargo containers while lifting them off lorries, removing the need for massive reference weights. Smaller spring balance setups are used to measure everyday light weights from 0 up to 100 grams.
Digital balance for fine accuracy
A digital balance measures tiny masses without reference weights and can detect every single milligram starting from 10 milligrams, such as 11, 12, or 13 milligrams. This level of precision is critical in pharmaceutical work, where a physical balance cannot measure intermediate values between 10 and 20 milligrams. For example, an exact dose of 1,000 milligrams of acetaminophen in paracetamol is required, because taking more than that amount can harm the liver and cause severe stomach pain.