two sets of questions

Next, consider just the closed loop containing the fixed reslator are! me lamp If Ze - 21, and there are no eris, the pos Fist Questions total zera Starting at point A and moving clockwise around the kop the current moves through the lamp. which is measured at =0.85 V Continuing to point B and then back up to complete the loop at A means going through the fixed resistor against the I In fig D, use Ohm's law to find the current through amminer A, flow of the current. This means the pd will be negative, although 2 The current through the cell in fig D is 1.35 A. Use your answer also 0.95 V. So in this consideration, V, = -085 V. from question 1 to show that the cuculi junction between the two ammeters in fig D conservin current. EV - V) + V4 - -0.05+ 0.85 - 0 3 Ex - EV Demonstrate by calculation that the lower loop in the circuit in fig D conserv crergy. Voltages rule with calculated pds 4 Find the emf of the cell in fig E. Potential differences are the product of currents passing through resistances, in order to use up electrical energy. Thus, each pd could be calculated from Ohm's law as V= /R. So this becomes 0.30 A R, = 750 10.38A 1017 20 0 1 - D.4SACA R. = 250 fig E Using the voltages circn rule. R = 5.00 Key definitions Electric current rule The algebraic sum of the currents entering a junction is er zero, El = 0 V = 4.5V Voltages circuit rule Around a closed loop, the algebraic sum of the emis is er fig D Confining Le = E/R. algebraic sum of the pds. " mula smound the upper closed EB = EIR Questions 1 A potential divider circuit supplied by an emf of BV has two resistors, R, = 125 01 and R, = 135 0. What will be the output voltage across Ry? 2 A potentiometer, as in fig F. is supplied by an emf of 15 V and has a 40 cm length of resistance wire. What voltage would be tapped off as Vout if the wiper was placed 10 cm from the top? 3 Draw a potential divider circuit, like that in fig G, which will drive a fan motor in a conservatory faster as it becomes hotter. (A standard thermistor has a higher resistance at lower temperatures.) 4 Fig H shows a length of resistance wire, with a contact that can rotate around a pivot to contact with more or less of the resistance wire. Explain how this represents a potential divider circuit and what will happen to the brightness of the lamp as the contact is rotated clockwise from the position shown. fig H