Resistance and Ohm's lawIB MYP Physics: Mind map

Exam questions on Resistance and Ohm's law

1. A technician in a workshop tests a resistor from a heating unit. She connects it to a power supply with a voltmeter and an ammeter. The voltmeter reads 12 V and the ammeter reads 0.60 A. The resistor stays at a constant temperature throughout the test.
   The technician doubles the potential difference to 24 V. Calculate the new current, assuming the resistor is ohmic at constant temperature.2 marks
2. A student plots current against potential difference for three components in turn: a fixed resistor, a filament lamp and a diode. She increases the potential difference from zero in small steps and then reverses the connections to test the diode in the opposite direction.
   Describe the shape of the current–potential difference graph for the fixed resistor and state what this shows about its resistance.2 marks
3. A group of students investigates how the length of a piece of nichrome wire affects its resistance. They connect the wire to a cell, with an ammeter and a voltmeter, and use a metre rule to change the length of wire in the circuit.
   Describe how the students can find the resistance of the wire at each length, and state one safety precaution.3 marks