A carbon resistor connected to a battery of 50V and 2A current is passing through it. If voltage is increased to 75V then current will be:
Correct answer: B. 3A
- A. 1.5A
- B. 3A
- C. 4.5A
- D. 6A
Explanation
Firstly, we'll calculate the resistance of the carbon resistor by using the formula Voltage= Current x Resistance. Once we have the resistance, we use it to calculate the current when voltage increases to 75V using the same formula. SInce we have a simple resistor and not a variable one, its resistance remains constant. First we calculate resistance of the resistor by using ohm's law : V=IR R=V/I =50/2 = 25ohm Since its a simple resistor and not a variable one hence its resistance remains constant Now we calculate the current through it when voltage changes from 50V to 75V I=V/R =75/25 = 3A ANS
This question appeared on the UHS MDCAT 2017 paper, which you can sit online with every answer explained.
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About Resistance and Resistivity
Resistance measures opposition to current in a conductor and follows R = V/I for an ohmic conductor, while resistivity is an intrinsic property of the material. Questions use R = ρL/A, examine effects of length, cross-sectional area and temperature, and distinguish resistance, resistivity, conductance and conductivity.
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