A-Level Physics Electricity

Define Resistance. [1 mark}

Ratio of current and p.d

Define potential diffference. [1 mark]

Work done from electrical supply per unit charge

Define electromotive force. [1 mark]

Work done to electrical supply per unit charge.

What is characteristic of forward bias when below 0.6 V in figure 1.

Positive voltage, initially resistance is very high and negliable current.

What happen to resistance of NTC thermistor when temperature increase. [1 mark]

Decrease

Define superconductivity. [1 mark]

Materials whose resistance becomes zero when their temperature is at or below critical temperature.

What happen to LDR’s resistance when the light intensity increase. [1 mark]

Decrease.

Define resistivity. [2 marks]

Resistance of a sample of material of unit length and unit cross-sectional area at a given temperature.

State ohm laws. [2 marks]

Current is directly proportional to potential difference in a metallic conductor while keep temperature and other physical properties the same.

Explain why superconductor is very useful. [2 marks]

No resistance.

Hence, no energy is wasted.

State two uses of superconductor. [2 marks]

Fusion reactors and MRI scanner

Cell is model by a long and short line.

Which line is represent positive and negative.

Long line is positive.

Short line is negative.

Cell is a negative and positive side.

Which direction electron going.

From negative to positive.

Kirchhoff’s First Rule: The sum of the currents flowing into a point is equal to the sum of the current flowing out of a point.

What has been conserver according to Kirchhoff’s First Rule.

Charge.