Physics

Problem

Four devices P, Q, R and S were tested at two different voltages. Their readings are listed below: • P:

(1\,\text{V},\;0.25\,\text{A})

and

(4\,\text{V},\;1.00\,\text{A})

• Q:

(2\,\text{V},\;0.40\,\text{A})

and

(6\,\text{V},\;1.10\,\text{A})

• R:

(1\,\text{V},\;0.30\,\text{A})

and

(4\,\text{V},\;1.60\,\text{A})

• S:

(2\,\text{V},\;0.50\,\text{A})

and

(6\,\text{V},\;1.60\,\text{A})

Which device behaves as an ohmic conductor? a) Device\;S b) None\;of\;the\;devices c) Device\;P d) Device\;Q

Intuitive explanation

An ohmic conductor obeys Ohm's law—its resistance $R = V/I$ stays constant across different voltages. The key is to calculate the resistance at both test points for each device; if the two values match, that device is ohmic. Non-ohmic devices (like filament bulbs) have resistance that changes with temperature as voltage increases.

Intuitive explanation

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