This English question involves literary analysis, grammar, or writing skills. The detailed response below provides a well-structured answer with supporting evidence and clear explanations.
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1.41 \Omega
Here is the solution to question 8 in English:
8. (a) (i) Ohm's Law states that the current flowing through a conductor between two points is directly proportional to the voltage across the two points, provided the temperature and other physical conditions remain constant. Mathematically, it is expressed as .
8. (a) (ii) To plot the graph of potential difference, , against current, : • Draw an x-axis (horizontal) for current (in amperes, A) and a y-axis (vertical) for potential difference (in volts, V). • Choose appropriate scales for each axis so that all data points can be represented. • Plot the given data points: , , , , , , , . • Draw the best straight line passing through the origin and the plotted points.
8. (a) (iii) Step 1: Calculate the gradient of the graph. The gradient is given by the formula . Using the points and from the table (representing the best straight line passing through the origin): Step 2: State the significance of the gradient. The gradient of a potential difference () versus current () graph represents the resistance of the conductor. The gradient is approximately . Its significance is the resistance of the conductor.
8. (a) (iv) Step 1: Use Ohm's Law and the calculated resistance. From Ohm's Law, . We calculated the resistance from the gradient. We want to find the current when . Step 2: Substitute the values and calculate the current. The current in the circuit when the potential difference is 7.5 V is approximately .
8. (b) (i) Electromotive force (e.m.f.) is the energy supplied by a source (such as a battery) per unit charge to drive the charge around a complete circuit. It is measured in volts (V) and represents the potential difference across the terminals of the source when no current is flowing.
8. (b) (ii) The resistance of a wire is given by the formula , where is resistivity, is length, and is cross-sectional area. If the wire is replaced by a thinner wire of the same material and length, its cross-sectional area decreases. A decrease in leads to an increase in resistance . According to Ohm's Law (), if the resistance increases and the battery voltage remains constant, the current will decrease.
8. (c) (i) The function of a fuse is to protect electrical circuits from overcurrents. It melts and breaks the circuit if the current exceeds a safe level, preventing damage to appliances and reducing fire hazards. It is connected in series with the live wire of the circuit.
8. (c) (ii) A fuse contains a thin wire made of a material with a low melting point. When the current flowing through the circuit exceeds the fuse's rated value, the wire heats up due to the Joule heating effect (). This heat causes the fuse wire to melt, creating an open circuit. This interruption stops the flow of current, thereby protecting appliances and preventing electrical hazards.
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8. (a) (i) Ohm's Law states that the current flowing through a conductor between two points is directly proportional to the voltage across the two points, provided the temperature and other physical conditions remain constant.
This English question involves literary analysis, grammar, or writing skills. The detailed response below provides a well-structured answer with supporting evidence and clear explanations.