Q3 A 200 resistor, a 300 resistor and a variable resistor are connected to a 6 V d.c. supply as illustrated in Fig 18.8.The variable resistor is initially set at 100 . (i) Calculate the current flowing through each resistor. (ii) What happens to current passing through the fixed resistors as its resistance of the variable resistor is increased?
Q4 A 150 resistor, an 800 resistor and a variable resistor set at its maximum resistance of 1 k are connected to a 12 V d.c. supply as illustrated in Fig 18.9. (i) Calculate the total resistance of the circuit. (ii) Calculate the current flowing through the 800 resistor. (iii) What happens to the potential difference across the 150 as its resistance of the variable resistor is lowered?
A potential divider, along with a fixed voltage power supply, can be used as a variable voltage power supply.The emf of the circuit equals the sum of all the potential differ- ences in the circuit. If a battery produces an emf of 12 V, regardless of how many resistors are in the circuit, the potential drops by 12 V across all the resistors together. If there is one resistor, the potential drops by the full 12 V across it.With two resistors
