Thermometer Practice Questions
20 free Thermometer practice questions for the General Science. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
What physical property of materials is most commonly exploited in the design of a traditional liquid-in-glass thermometer?
- A Thermal conductivity
- B Thermal expansion
- C Specific heat capacity
- D Refractive index
Correct answer: Thermal expansion
Liquid-in-glass thermometers work on the principle of thermal expansion. As the temperature increases, the kinetic energy of the liquid molecules increases, causing the liquid to expand and rise up the narrow capillary tube.
Why is a clinical thermometer designed with a 'kink' or constriction in its capillary tube?
- A To keep the glass tube from cracking when internal pressure rises during measurement.
- B To increase the sensitivity of the temperature readings.
- C To prevent the mercury from falling back into the bulb immediately after use.
- D To make the thermometer easier to hold and grip.
Correct answer: To prevent the mercury from falling back into the bulb immediately after use.
The constriction breaks the mercury thread as it cools and contracts. This holds the highest reached temperature in place, allowing the healthcare provider to read the measurement even after the thermometer is removed from the patient.
Which liquid is typically used in thermometers designed to measure extremely low temperatures, such as those in arctic environments?
- A Mercury
- B Ethyl alcohol
- C Water
- D Liquid nitrogen
Correct answer: Ethyl alcohol
Mercury freezes at -38.8°C, making it useless for very cold climates. Alcohol has a much lower freezing point (approximately -114°C), allowing it to remain in a liquid state for low-temperature measurements.
What is the standard range of temperature typically found on a clinical thermometer used for human body temperature?
- A 0°C to 100°C
- B 35°C to 42°C
- C 20°C to 50°C
- D 37°C to 98°C
Correct answer: 35°C to 42°C
Since the human body's viable temperature range is very narrow, clinical thermometers are calibrated specifically between 35°C and 42°C (or 95°F to 108°F) to provide high precision within that range.
Which type of thermometer determines temperature by tracking how strongly a platinum wire opposes an electric current?
- A Bimetallic strip dial thermometer
- B Constant volume gas thermometer
- C Resistance temperature detector
- D Infrared thermometer
Correct answer: Resistance temperature detector
An RTD works on the principle that the electrical resistance of metals, such as platinum, increases predictably with temperature. By measuring this resistance, the temperature can be calculated with high accuracy.
An infrared thermometer, often used for non-contact temperature measurement, detects which of the following?
- A Convection currents from the object
- B Visible light reflected from the object's surface
- C Thermal radiation emitted by the object
- D Sound waves vibrating through the air
Correct answer: Thermal radiation emitted by the object
Every object with a temperature above absolute zero emits infrared radiation. The thermometer uses a lens to focus this radiation onto a detector, which converts the energy into an electrical signal representing the temperature.
What is the primary advantage of using mercury in laboratory thermometers over other liquids?
- A It is non-toxic and completely safe to handle.
- B It expands uniformly and does not stick to the glass.
- C It is transparent, so the level inside the tube is easy to read.
- D It has a very low boiling point compared with water.
Correct answer: It expands uniformly and does not stick to the glass.
Mercury is an ideal thermometric liquid because it expands linearly with temperature, is opaque (easy to read), and has low surface tension, preventing it from wetting the walls of the capillary tube.
Which thermometer is considered the most accurate for scientific calibration and is used as a standard in laboratories?
- A Clinical thermometer
- B Constant-volume gas thermometer
- C Digital thermistor probe
- D Mercury-in-glass laboratory thermometer
Correct answer: Constant-volume gas thermometer
Gas thermometers, particularly constant-volume ones, are used as primary standards because gases expand more uniformly than liquids. They are used to calibrate other types of thermometers.
A bimetallic strip thermometer operates based on which principle?
- A Different metals have different rates of thermal expansion.
- B Metals change color as they get hotter.
- C The melting point of an alloy is lower than its components.
- D Electric current flows better through cold metals.
Correct answer: Different metals have different rates of thermal expansion.
A bimetallic strip consists of two different metals bonded together. Because they expand at different rates when heated, the strip bends, and this mechanical movement is used to move a needle on a temperature scale.
What happens to the liquid level in a thermometer initially if it is suddenly plunged into very hot water?
- A It rises immediately.
- B It falls slightly before rising.
- C It stays the same for a few minutes.
- D The glass shatters instantly.
Correct answer: It falls slightly before rising.
When first plunged into hot water, the glass bulb expands before the heat reaches the liquid inside. This slight increase in the bulb's volume causes the liquid level to drop momentarily before the liquid itself begins to expand and rise.
Which instrument is used specifically for measuring very high temperatures, such as those in a furnace?
- A Alcohol thermometer
- B Hygrometer
- C Six's thermometer
- D Optical pyrometer
Correct answer: Optical pyrometer
An optical pyrometer is a remote-sensing instrument that measures very high temperatures from the thermal radiation a hot body emits. It is essential in furnaces and other industrial settings where physical contact with the object is impossible.
Which temperature scale has its zero point at the freezing point of water and 100 at the boiling point of water at standard pressure?
- A Kelvin
- B Fahrenheit
- C Celsius
- D Rankine
Correct answer: Celsius
The Celsius scale, formerly known as the centigrade scale, is based on 0°C for the freezing point of water and 100°C for the boiling point. It is the most widely used scale for everyday temperature measurement globally.
What is the purpose of the 'Six's thermometer'?
- A To measure the average air temperature over a full twenty-four hour period.
- B To measure humidity using wet-bulb and dry-bulb readings.
- C To measure the temperature of seawater at great depths.
- D To record the maximum and minimum temperatures reached during a period.
Correct answer: To record the maximum and minimum temperatures reached during a period.
Also known as a maximum-minimum thermometer, Six's thermometer uses two scales and small markers (indices) to record the highest and lowest temperatures that occurred since the last reset, typically over a 24-hour period.
In digital thermometers, the sensor is often a 'thermistor'. What does this term mean?
- A A thermal transistor
- B A heat-driven voltage source
- C A capacitor that stores thermal energy
- D A thermally sensitive resistor
Correct answer: A thermally sensitive resistor
A thermistor is a type of resistor whose resistance is highly dependent on temperature. In most digital thermometers, the change in resistance is converted into a digital temperature reading by an internal circuit.
Why is it dangerous to use a clinical thermometer to measure the temperature of boiling water?
- A The mercury will freeze.
- B The intense heat of boiling water will soften and melt the thin glass stem.
- C The expansion of mercury will exceed the narrow range and burst the bulb.
- D It will give an inaccurate reading because of the kink.
Correct answer: The expansion of mercury will exceed the narrow range and burst the bulb.
Clinical thermometers only go up to about 42°C. Boiling water (100°C) would cause the mercury to expand far beyond the capacity of the capillary tube, creating enough pressure to shatter the glass bulb.
Which thermometer uses two dissimilar metals joined at two junctions to generate a voltage proportional to the temperature difference?
- A Bimetallic strip
- B Resistance thermometer
- C Thermistor
- D Thermocouple
Correct answer: Thermocouple
A thermocouple works based on the Seebeck effect. When there is a temperature difference between the two junctions of the dissimilar metals, a small electric voltage is produced, which can be measured and calibrated to temperature.
Why is water not used as a thermometric liquid in common thermometers?
- A It conducts heat too slowly to respond to quick temperature changes.
- B It is too heavy for the glass tube.
- C It does not respond to heat changes.
- D It has a non-uniform expansion and a narrow liquid range.
Correct answer: It has a non-uniform expansion and a narrow liquid range.
Water has a narrow liquid range (0°C to 100°C) and exhibits anomalous expansion (it contracts when heated from 0°C to 4°C). This non-linear behavior makes it unsuitable for accurate temperature scales.
Absolute zero, the lowest temperature theoretically possible, corresponds to what reading on the Celsius scale?
- A 0 °C
- B -100 °C
- C -459.67 °C
- D -273.15 °C
Correct answer: -273.15 °C
Absolute zero is 0 K on the Kelvin scale, which equals -273.15 °C. It is the theoretical temperature at which all molecular motion stops. The value -459.67 is the same point expressed in degrees Fahrenheit.
The speed of response of a thermometer depends mainly on which factor?
- A The thickness of the glass bulb and the surface area
- B The total length of the capillary stem above the bulb
- C The color of the thermometric liquid
- D The atmospheric pressure outside
Correct answer: The thickness of the glass bulb and the surface area
A thin glass bulb allows heat to transfer to the liquid more quickly, and a larger surface area relative to the volume of liquid increases the rate of heat exchange, resulting in a faster reading.
How is a digital ear thermometer (tympanic thermometer) used to take a reading?
- A By detecting infrared radiation from the eardrum.
- B By measuring the resistance of the ear canal.
- C By using a bimetallic strip that touches the ear.
- D By measuring the sound waves bouncing off the eardrum.
Correct answer: By detecting infrared radiation from the eardrum.
Tympanic thermometers measure the infrared energy emitted from the eardrum and surrounding tissue. Since the eardrum shares the same blood supply as the hypothalamus (the body's temperature control center), it provides an accurate core temperature reading.