An engineer is designing a device that requires a precise and constant temperature to incubate bacterial cultures. Which principle should primarily guide the choice of the heating element for this device, considering the applications of the heating effect of current?
Using a material with suitable resistance to produce sufficient heat
By Joule's law of heating, the heat produced in a conductor is \(H = I^{2}Rt\). For a fixed supply, the heat produced depends on the resistance of the heating element, so the element must be chosen with the right resistance.
An incubator needs a steady, controlled amount of heat, enough to hold the cultures at the required temperature but not more. A material with suitable resistance (for example nichrome, which also does not oxidise easily when hot) produces sufficient heat steadily, and the temperature can then be held constant with a thermostat.
Increasing the current continuously would make the heat keep rising, so the temperature would not stay constant and could damage the cultures. A low-resistance material, or one that prevents heat production, would not provide the heat the device needs.
Hence, Using a material with suitable resistance to produce sufficient heat.
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Important Questions from Current Electricity
- In a parallel combination of resistors, which of the following quantities remains the same across all the resistors?
- Which of the following statements is/are true for a domestic circuit?
(i) All the appliances are connected in parallel.
(ii) The live wire in the domestic circuit has green insulation on it.
(iii) A fuse connected to the circuit allows excessive current to pass through the appliances.
(iv) The neutral wire in the domestic circuits has black insulation on it. A science teacher asks students to measure the current through a bulb using an ammeter. What precaution must the students follow?
- Which characteristic of parallel circuits makes them advantageous over series circuits for connecting multiple electrical gadgets in a house?
- In a domestic electric circuit, the main purpose of a FUSE is ________.
